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 $196.36   4.224%   $204.6542   $204.65   $204.65   $204.70  
  Purchase #2 $106.54   10.729%   $117.9707   $117.97   $117.95   $118.00  
  Purchase #3 $211.33   7.855%   $227.93   $227.93   $227.95   $227.90  
  Purchase #4 $211.35   9.222%   $230.8407   $230.84   $230.85   $230.80  
  Purchase #5 $229.82   7.270%   $246.5279   $246.53   $246.55   $246.50  
  Purchase #6 $151.52   9.872%   $166.4781   $166.48   $166.50   $166.50  
  Purchase #7 $233.55   13.851%   $265.899   $265.90   $265.90   $265.90  
  7 purchase totals = $1,340.47       $1,460.3006   $1,460.30   $1,460.35   $1,460.30