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 $56.54   9.761%   $62.0589   $62.06   $62.05   $62.10  
  Purchase #2 $135.75   13.164%   $153.6201   $153.62   $153.60   $153.60  
  Purchase #3 $113.74   6.121%   $120.702   $120.70   $120.70   $120.70  
  Purchase #4 $60.58   9.277%   $66.2   $66.20   $66.20   $66.20  
  Purchase #5 $88.55   7.504%   $95.1948   $95.19   $95.20   $95.20  
  Purchase #6 $181.57   11.793%   $202.9826   $202.98   $203.00   $203.00  
  Purchase #7 $194.87   4.522%   $203.682   $203.68   $203.70   $203.70  
  7 purchase totals = $831.60       $904.4404   $904.43   $904.45   $904.50