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	$6.96	5.665%	$7.3543	$7.35	$7.35	$7.40
Purchase #2	$140.39	8.428%	$152.2221	$152.22	$152.20	$152.20
Purchase #3	$202.87	5.218%	$213.4558	$213.46	$213.45	$213.50
Purchase #4	$101.26	3.250%	$104.551	$104.55	$104.55	$104.60
Purchase #5	$169.91	12.539%	$191.215	$191.22	$191.20	$191.20
Purchase #6	$108.55	3.743%	$112.613	$112.61	$112.60	$112.60
Purchase #7	$236.26	8.313%	$255.9003	$255.90	$255.90	$255.90
7 purchase totals =	$966.20		$1,037.3115	$1,037.31	$1,037.25	$1,037.40