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 $56.53   9.603%   $61.9586   $61.96   $61.95   $62.00  
  Purchase #2 $29.33   13.208%   $33.2039   $33.20   $33.20   $33.20  
  Purchase #3 $109.48   10.314%   $120.7718   $120.77   $120.75   $120.80  
  Purchase #4 $15.57   7.363%   $16.7164   $16.72   $16.70   $16.70  
  Purchase #5 $91.55   4.667%   $95.8226   $95.82   $95.80   $95.80  
  Purchase #6 $234.81   7.162%   $251.6271   $251.63   $251.65   $251.60  
  Purchase #7 $195.85   10.584%   $216.5788   $216.58   $216.60   $216.60  
  7 purchase totals = $733.12       $796.6792   $796.68   $796.65   $796.70