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 $62.35   11.782%   $69.6961   $69.70   $69.70   $69.70  
  Purchase #2 $156.58   6.849%   $167.3042   $167.30   $167.30   $167.30  
  Purchase #3 $220.86   13.763%   $251.257   $251.26   $251.25   $251.30  
  Purchase #4 $90.74   4.436%   $94.7652   $94.77   $94.75   $94.80  
  Purchase #5 $174.75   7.588%   $188.01   $188.01   $188.00   $188.00  
  Purchase #6 $242.39   5.799%   $256.4462   $256.45   $256.45   $256.40  
  Purchase #7 $30.69   6.827%   $32.7852   $32.79   $32.80   $32.80  
  7 purchase totals = $978.36       $1,060.2639   $1,060.28   $1,060.25   $1,060.30