Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
  Case Tag  
Price  
Sales  
Tax %  
Raw Total  
Incl. Sales Tax  
Rounded  
to Penny  
Rounded  
to Nickel  
Rounded  
to Dime  
  Purchase #1 $144.26   5.352%   $151.9808   $151.98   $152.00   $152.00  
  Purchase #2 $118.58   12.434%   $133.3242   $133.32   $133.30   $133.30  
  Purchase #3 $105.71   11.325%   $117.6817   $117.68   $117.70   $117.70  
  Purchase #4 $161.45   5.463%   $170.27   $170.27   $170.25   $170.30  
  Purchase #5 $204.54   6.799%   $218.4467   $218.45   $218.45   $218.40  
  Purchase #6 $219.42   12.539%   $246.9331   $246.93   $246.95   $246.90  
  Purchase #7 $222.26   6.156%   $235.9423   $235.94   $235.95   $235.90  
  7 purchase totals = $1,176.22       $1,274.5788   $1,274.57   $1,274.60   $1,274.50