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 $184.71   5.409%   $194.701   $194.70   $194.70   $194.70  
  Purchase #2 $169.76   7.174%   $181.9386   $181.94   $181.95   $181.90  
  Purchase #3 $43.53   4.519%   $45.4971   $45.50   $45.50   $45.50  
  Purchase #4 $148.71   11.701%   $166.1106   $166.11   $166.10   $166.10  
  Purchase #5 $228.39   5.422%   $240.7733   $240.77   $240.75   $240.80  
  Purchase #6 $216.57   7.606%   $233.0423   $233.04   $233.05   $233.00  
  Purchase #7 $179.55   7.687%   $193.352   $193.35   $193.35   $193.40  
  7 purchase totals = $1,171.22       $1,255.4149   $1,255.41   $1,255.40   $1,255.40