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 $203.36   3.763%   $211.0124   $211.01   $211.00   $211.00  
  Purchase #2 $116.74   9.390%   $127.7019   $127.70   $127.70   $127.70  
  Purchase #3 $203.32   4.790%   $213.059   $213.06   $213.05   $213.10  
  Purchase #4 $23.31   9.578%   $25.5426   $25.54   $25.55   $25.50  
  Purchase #5 $168.49   5.376%   $177.548   $177.55   $177.55   $177.50  
  Purchase #6 $146.35   5.380%   $154.2236   $154.22   $154.20   $154.20  
  Purchase #7 $210.42   8.354%   $227.9985   $228.00   $228.00   $228.00  
  7 purchase totals = $1,071.99       $1,137.0860   $1,137.08   $1,137.05   $1,137.00