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 $191.81   6.492%   $204.2623   $204.26   $204.25   $204.30  
  Purchase #2 $219.74   4.839%   $230.3732   $230.37   $230.35   $230.40  
  Purchase #3 $87.65   9.849%   $96.2826   $96.28   $96.30   $96.30  
  Purchase #4 $75.68   11.842%   $84.642   $84.64   $84.65   $84.60  
  Purchase #5 $193.77   3.260%   $200.0869   $200.09   $200.10   $200.10  
  Purchase #6 $156.37   4.644%   $163.6318   $163.63   $163.65   $163.60  
  Purchase #7 $33.37   5.585%   $35.2337   $35.23   $35.25   $35.20  
  7 purchase totals = $958.39       $1,014.5125   $1,014.50   $1,014.55   $1,014.50