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 $71.48   4.198%   $74.4807   $74.48   $74.50   $74.50  
  Purchase #2 $195.97   5.246%   $206.2506   $206.25   $206.25   $206.30  
  Purchase #3 $22.48   4.112%   $23.4044   $23.40   $23.40   $23.40  
  Purchase #4 $171.37   10.771%   $189.8283   $189.83   $189.85   $189.80  
  Purchase #5 $164.43   5.245%   $173.0544   $173.05   $173.05   $173.10  
  Purchase #6 $210.54   11.651%   $235.07   $235.07   $235.05   $235.10  
  Purchase #7 $120.94   7.765%   $130.331   $130.33   $130.35   $130.30  
  7 purchase totals = $957.21       $1,032.4194   $1,032.41   $1,032.45   $1,032.50