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 $154.74   13.570%   $175.7382   $175.74   $175.75   $175.70  
  Purchase #2 $108.83   13.459%   $123.4774   $123.48   $123.50   $123.50  
  Purchase #3 $64.27   11.560%   $71.6996   $71.70   $71.70   $71.70  
  Purchase #4 $160.81   7.565%   $172.9753   $172.98   $173.00   $173.00  
  Purchase #5 $207.67   9.184%   $226.7424   $226.74   $226.75   $226.70  
  Purchase #6 $77.26   5.577%   $81.5688   $81.57   $81.55   $81.60  
  Purchase #7 $167.64   7.604%   $180.3873   $180.39   $180.40   $180.40  
  7 purchase totals = $941.22       $1,032.5890   $1,032.60   $1,032.65   $1,032.60