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 $191.84   5.593%   $202.5696   $202.57   $202.55   $202.60  
  Purchase #2 $98.85   5.507%   $104.2937   $104.29   $104.30   $104.30  
  Purchase #3 $115.51   12.126%   $129.5167   $129.52   $129.50   $129.50  
  Purchase #4 $58.41   8.171%   $63.1827   $63.18   $63.20   $63.20  
  Purchase #5 $184.95   4.497%   $193.2672   $193.27   $193.25   $193.30  
  Purchase #6 $153.72   13.210%   $174.0264   $174.03   $174.05   $174.00  
  Purchase #7 $186.66   5.235%   $196.4317   $196.43   $196.45   $196.40  
  7 purchase totals = $989.94       $1,063.2880   $1,063.29   $1,063.30   $1,063.30