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 $214.66   9.832%   $235.7654   $235.77   $235.75   $235.80  
  Purchase #2 $184.47   9.352%   $201.7216   $201.72   $201.70   $201.70  
  Purchase #3 $214.77   4.293%   $223.9901   $223.99   $224.00   $224.00  
  Purchase #4 $30.51   12.833%   $34.4253   $34.43   $34.45   $34.40  
  Purchase #5 $151.71   4.585%   $158.6659   $158.67   $158.65   $158.70  
  Purchase #6 $73.29   9.425%   $80.1976   $80.20   $80.20   $80.20  
  Purchase #7 $145.49   9.798%   $159.7451   $159.75   $159.75   $159.70  
  7 purchase totals = $1,014.90       $1,094.5110   $1,094.53   $1,094.50   $1,094.50