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 $84.44   13.733%   $96.0361   $96.04   $96.05   $96.00  
  Purchase #2 $13.47   9.408%   $14.7373   $14.74   $14.75   $14.70  
  Purchase #3 $167.62   9.652%   $183.7987   $183.80   $183.80   $183.80  
  Purchase #4 $238.28   3.509%   $246.6412   $246.64   $246.65   $246.60  
  Purchase #5 $244.79   12.276%   $274.8404   $274.84   $274.85   $274.80  
  Purchase #6 $12.73   10.385%   $14.052   $14.05   $14.05   $14.10  
  Purchase #7 $172.52   9.593%   $189.0698   $189.07   $189.05   $189.10  
  7 purchase totals = $933.85       $1,019.1755   $1,019.18   $1,019.20   $1,019.10