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 $60.58   11.482%   $67.5358   $67.54   $67.55   $67.50  
  Purchase #2 $94.63   10.415%   $104.4857   $104.49   $104.50   $104.50  
  Purchase #3 $143.40   8.590%   $155.7181   $155.72   $155.70   $155.70  
  Purchase #4 $150.55   12.722%   $169.703   $169.70   $169.70   $169.70  
  Purchase #5 $192.56   5.287%   $202.7406   $202.74   $202.75   $202.70  
  Purchase #6 $196.67   7.639%   $211.6936   $211.69   $211.70   $211.70  
  Purchase #7 $197.52   8.559%   $214.4257   $214.43   $214.45   $214.40  
  7 purchase totals = $1,035.91       $1,126.3025   $1,126.31   $1,126.35   $1,126.20