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 $74.61   3.548%   $77.2572   $77.26   $77.25   $77.30  
  Purchase #2 $247.89   9.366%   $271.1074   $271.11   $271.10   $271.10  
  Purchase #3 $195.30   7.717%   $210.3713   $210.37   $210.35   $210.40  
  Purchase #4 $189.52   12.454%   $213.1228   $213.12   $213.10   $213.10  
  Purchase #5 $88.69   11.601%   $98.9789   $98.98   $99.00   $99.00  
  Purchase #6 $238.53   13.764%   $271.3613   $271.36   $271.35   $271.40  
  Purchase #7 $42.81   3.658%   $44.376   $44.38   $44.40   $44.40  
  7 purchase totals = $1,077.35       $1,186.5749   $1,186.58   $1,186.55   $1,186.70