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 $77.28   11.222%   $85.9524   $85.95   $85.95   $86.00  
  Purchase #2 $198.51   8.814%   $216.0067   $216.01   $216.00   $216.00  
  Purchase #3 $91.42   5.433%   $96.3868   $96.39   $96.40   $96.40  
  Purchase #4 $210.36   10.557%   $232.5677   $232.57   $232.55   $232.60  
  Purchase #5 $110.56   5.530%   $116.674   $116.67   $116.65   $116.70  
  Purchase #6 $174.46   3.636%   $180.8034   $180.80   $180.80   $180.80  
  Purchase #7 $235.79   5.473%   $248.6948   $248.69   $248.70   $248.70  
  7 purchase totals = $1,098.38       $1,177.0858   $1,177.08   $1,177.05   $1,177.20