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 $189.67   3.151%   $195.6465   $195.65   $195.65   $195.60  
  Purchase #2 $96.57   12.455%   $108.5978   $108.60   $108.60   $108.60  
  Purchase #3 $220.63   9.501%   $241.5921   $241.59   $241.60   $241.60  
  Purchase #4 $95.29   9.789%   $104.6179   $104.62   $104.60   $104.60  
  Purchase #5 $157.31   10.798%   $174.2963   $174.30   $174.30   $174.30  
  Purchase #6 $167.39   6.371%   $178.0544   $178.05   $178.05   $178.10  
  Purchase #7 $99.52   3.257%   $102.7614   $102.76   $102.75   $102.80  
  7 purchase totals = $1,026.38       $1,105.5664   $1,105.57   $1,105.55   $1,105.60