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 $211.47   4.348%   $220.6647   $220.66   $220.65   $220.70  
  Purchase #2 $27.87   6.415%   $29.6579   $29.66   $29.65   $29.70  
  Purchase #3 $34.96   7.426%   $37.5561   $37.56   $37.55   $37.60  
  Purchase #4 $229.52   7.196%   $246.0363   $246.04   $246.05   $246.00  
  Purchase #5 $228.72   13.383%   $259.3296   $259.33   $259.35   $259.30  
  Purchase #6 $222.35   4.523%   $232.4069   $232.41   $232.40   $232.40  
  Purchase #7 $58.95   13.581%   $66.956   $66.96   $66.95   $67.00  
  7 purchase totals = $1,013.84       $1,092.6075   $1,092.62   $1,092.60   $1,092.70