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	$112.25	10.493%	$124.0284	$124.03	$124.05	$124.00
Purchase #2	$83.41	8.149%	$90.2071	$90.21	$90.20	$90.20
Purchase #3	$190.58	7.125%	$204.1588	$204.16	$204.15	$204.20
Purchase #4	$221.59	4.191%	$230.8768	$230.88	$230.90	$230.90
Purchase #5	$56.41	5.872%	$59.7224	$59.72	$59.70	$59.70
Purchase #6	$176.43	4.771%	$184.8475	$184.85	$184.85	$184.80
Purchase #7	$183.56	12.424%	$206.3655	$206.37	$206.35	$206.40
7 purchase totals =	$1,024.23		$1,100.2065	$1,100.22	$1,100.20	$1,100.20