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 $86.56   10.509%   $95.6566   $95.66   $95.65   $95.70  
  Purchase #2 $84.64   12.528%   $95.2437   $95.24   $95.25   $95.20  
  Purchase #3 $90.27   10.273%   $99.5434   $99.54   $99.55   $99.50  
  Purchase #4 $96.51   10.148%   $106.3038   $106.30   $106.30   $106.30  
  Purchase #5 $211.35   11.479%   $235.6109   $235.61   $235.60   $235.60  
  Purchase #6 $126.61   9.192%   $138.248   $138.25   $138.25   $138.20  
  Purchase #7 $149.47   11.468%   $166.6112   $166.61   $166.60   $166.60  
  7 purchase totals = $845.41       $937.2176   $937.21   $937.20   $937.10