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 $244.42   12.527%   $275.0385   $275.04   $275.05   $275.00  
  Purchase #2 $201.67   4.212%   $210.1643   $210.16   $210.15   $210.20  
  Purchase #3 $164.52   7.403%   $176.6994   $176.70   $176.70   $176.70  
  Purchase #4 $22.84   10.141%   $25.1562   $25.16   $25.15   $25.20  
  Purchase #5 $85.70   11.210%   $95.307   $95.31   $95.30   $95.30  
  Purchase #6 $211.94   6.424%   $225.555   $225.56   $225.55   $225.60  
  Purchase #7 $94.45   12.669%   $106.4159   $106.42   $106.40   $106.40  
  7 purchase totals = $1,025.54       $1,114.3363   $1,114.35   $1,114.30   $1,114.40