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 $195.97   3.554%   $202.9348   $202.93   $202.95   $202.90  
  Purchase #2 $73.85   13.151%   $83.562   $83.56   $83.55   $83.60  
  Purchase #3 $200.78   11.143%   $223.1529   $223.15   $223.15   $223.20  
  Purchase #4 $169.84   4.516%   $177.51   $177.51   $177.50   $177.50  
  Purchase #5 $168.59   11.323%   $187.6794   $187.68   $187.70   $187.70  
  Purchase #6 $147.29   5.554%   $155.4705   $155.47   $155.45   $155.50  
  Purchase #7 $42.71   11.264%   $47.5209   $47.52   $47.50   $47.50  
  7 purchase totals = $999.03       $1,077.8305   $1,077.82   $1,077.80   $1,077.90