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 $65.98   11.562%   $73.6086   $73.61   $73.60   $73.60  
  Purchase #2 $188.59   9.133%   $205.8139   $205.81   $205.80   $205.80  
  Purchase #3 $227.52   4.241%   $237.1691   $237.17   $237.15   $237.20  
  Purchase #4 $167.91   7.859%   $181.106   $181.11   $181.10   $181.10  
  Purchase #5 $212.53   8.613%   $230.8352   $230.84   $230.85   $230.80  
  Purchase #6 $9.55   7.787%   $10.2937   $10.29   $10.30   $10.30  
  Purchase #7 $229.68   13.369%   $260.3859   $260.39   $260.40   $260.40  
  7 purchase totals = $1,101.76       $1,199.2124   $1,199.22   $1,199.20   $1,199.20