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 $173.60   11.795%   $194.0761   $194.08   $194.10   $194.10  
  Purchase #2 $250.45   6.728%   $267.3003   $267.30   $267.30   $267.30  
  Purchase #3 $39.94   3.732%   $41.4306   $41.43   $41.45   $41.40  
  Purchase #4 $48.99   12.710%   $55.2166   $55.22   $55.20   $55.20  
  Purchase #5 $119.72   9.589%   $131.2   $131.20   $131.20   $131.20  
  Purchase #6 $193.36   11.804%   $216.1842   $216.18   $216.20   $216.20  
  Purchase #7 $112.93   5.476%   $119.114   $119.11   $119.10   $119.10  
  7 purchase totals = $938.99       $1,024.5218   $1,024.52   $1,024.55   $1,024.50