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 $70.29   7.561%   $75.6046   $75.60   $75.60   $75.60  
  Purchase #2 $202.73   11.570%   $226.1859   $226.19   $226.20   $226.20  
  Purchase #3 $62.48   6.760%   $66.7036   $66.70   $66.70   $66.70  
  Purchase #4 $220.91   7.384%   $237.222   $237.22   $237.20   $237.20  
  Purchase #5 $135.89   4.605%   $142.1477   $142.15   $142.15   $142.10  
  Purchase #6 $109.49   9.298%   $119.6704   $119.67   $119.65   $119.70  
  Purchase #7 $201.49   3.551%   $208.6449   $208.64   $208.65   $208.60  
  7 purchase totals = $1,003.28       $1,076.1791   $1,076.17   $1,076.15   $1,076.10