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 $141.92   7.503%   $152.5683   $152.57   $152.55   $152.60  
  Purchase #2 $53.45   4.472%   $55.8403   $55.84   $55.85   $55.80  
  Purchase #3 $104.90   9.511%   $114.877   $114.88   $114.90   $114.90  
  Purchase #4 $233.85   4.127%   $243.501   $243.50   $243.50   $243.50  
  Purchase #5 $91.49   11.717%   $102.2099   $102.21   $102.20   $102.20  
  Purchase #6 $225.84   6.250%   $239.955   $239.96   $239.95   $240.00  
  Purchase #7 $243.91   12.813%   $275.1622   $275.16   $275.15   $275.20  
  7 purchase totals = $1,095.36       $1,184.1137   $1,184.12   $1,184.10   $1,184.20