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 $187.62   3.294%   $193.8002   $193.80   $193.80   $193.80  
  Purchase #2 $189.65   12.133%   $212.6602   $212.66   $212.65   $212.70  
  Purchase #3 $17.72   9.266%   $19.3619   $19.36   $19.35   $19.40  
  Purchase #4 $166.28   13.415%   $188.5865   $188.59   $188.60   $188.60  
  Purchase #5 $87.96   6.793%   $93.9351   $93.94   $93.95   $93.90  
  Purchase #6 $188.99   4.716%   $197.9028   $197.90   $197.90   $197.90  
  Purchase #7 $163.75   3.326%   $169.1963   $169.20   $169.20   $169.20  
  7 purchase totals = $1,001.97       $1,075.4430   $1,075.45   $1,075.45   $1,075.50