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 $73.66   5.122%   $77.4329   $77.43   $77.45   $77.40  
  Purchase #2 $92.95   5.644%   $98.1961   $98.20   $98.20   $98.20  
  Purchase #3 $26.58   11.119%   $29.5354   $29.54   $29.55   $29.50  
  Purchase #4 $61.27   3.712%   $63.5443   $63.54   $63.55   $63.50  
  Purchase #5 $202.72   5.740%   $214.3561   $214.36   $214.35   $214.40  
  Purchase #6 $230.30   13.217%   $260.7388   $260.74   $260.75   $260.70  
  Purchase #7 $139.87   8.121%   $151.2288   $151.23   $151.25   $151.20  
  7 purchase totals = $827.35       $895.0324   $895.04   $895.10   $894.90