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 $208.54   11.400%   $232.3136   $232.31   $232.30   $232.30  
  Purchase #2 $187.99   12.442%   $211.3797   $211.38   $211.40   $211.40  
  Purchase #3 $159.43   5.309%   $167.8941   $167.89   $167.90   $167.90  
  Purchase #4 $60.97   11.261%   $67.8358   $67.84   $67.85   $67.80  
  Purchase #5 $85.84   11.474%   $95.6893   $95.69   $95.70   $95.70  
  Purchase #6 $126.61   10.801%   $140.2851   $140.29   $140.30   $140.30  
  Purchase #7 $231.48   9.802%   $254.1697   $254.17   $254.15   $254.20  
  7 purchase totals = $1,060.86       $1,169.5673   $1,169.57   $1,169.60   $1,169.60