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 $151.94   11.285%   $169.0864   $169.09   $169.10   $169.10  
  Purchase #2 $205.81   5.281%   $216.6788   $216.68   $216.70   $216.70  
  Purchase #3 $41.56   3.551%   $43.0358   $43.04   $43.05   $43.00  
  Purchase #4 $43.37   7.655%   $46.69   $46.69   $46.70   $46.70  
  Purchase #5 $246.40   11.475%   $274.6744   $274.67   $274.65   $274.70  
  Purchase #6 $162.97   5.472%   $171.8877   $171.89   $171.90   $171.90  
  Purchase #7 $124.27   11.546%   $138.6182   $138.62   $138.60   $138.60  
  7 purchase totals = $976.32       $1,060.6713   $1,060.68   $1,060.70   $1,060.70