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 $85.95   7.210%   $92.147   $92.15   $92.15   $92.10  
  Purchase #2 $99.64   10.656%   $110.2576   $110.26   $110.25   $110.30  
  Purchase #3 $82.98   3.159%   $85.6013   $85.60   $85.60   $85.60  
  Purchase #4 $74.77   6.539%   $79.6592   $79.66   $79.65   $79.70  
  Purchase #5 $79.97   10.690%   $88.5188   $88.52   $88.50   $88.50  
  Purchase #6 $57.95   3.445%   $59.9464   $59.95   $59.95   $59.90  
  Purchase #7 $223.77   7.285%   $240.0716   $240.07   $240.05   $240.10  
  7 purchase totals = $705.03       $756.2019   $756.21   $756.15   $756.20