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	$174.44	9.344%	$190.7397	$190.74	$190.75	$190.70
Purchase #2	$242.59	4.438%	$253.3561	$253.36	$253.35	$253.40
Purchase #3	$67.74	3.335%	$69.9991	$70.00	$70.00	$70.00
Purchase #4	$25.49	11.267%	$28.362	$28.36	$28.35	$28.40
Purchase #5	$174.98	13.274%	$198.2068	$198.21	$198.20	$198.20
Purchase #6	$102.46	8.562%	$111.2326	$111.23	$111.25	$111.20
Purchase #7	$246.64	11.739%	$275.5931	$275.59	$275.60	$275.60
7 purchase totals =	$1,034.34		$1,127.4894	$1,127.49	$1,127.50	$1,127.50