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 $214.77   5.490%   $226.5609   $226.56   $226.55   $226.60  
  Purchase #2 $32.58   13.578%   $37.0037   $37.00   $37.00   $37.00  
  Purchase #3 $145.38   4.279%   $151.6008   $151.60   $151.60   $151.60  
  Purchase #4 $124.47   7.341%   $133.6073   $133.61   $133.60   $133.60  
  Purchase #5 $248.68   9.203%   $271.566   $271.57   $271.55   $271.60  
  Purchase #6 $216.45   9.581%   $237.1881   $237.19   $237.20   $237.20  
  Purchase #7 $172.65   12.669%   $194.523   $194.52   $194.50   $194.50  
  7 purchase totals = $1,154.98       $1,252.0498   $1,252.05   $1,252.00   $1,252.10