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	$225.36	3.494%	$233.2341	$233.23	$233.25	$233.20
Purchase #2	$243.29	5.284%	$256.1454	$256.15	$256.15	$256.10
Purchase #3	$23.32	12.196%	$26.1641	$26.16	$26.15	$26.20
Purchase #4	$48.62	10.819%	$53.8802	$53.88	$53.90	$53.90
Purchase #5	$55.83	6.719%	$59.5812	$59.58	$59.60	$59.60
Purchase #6	$211.46	8.762%	$229.9881	$229.99	$230.00	$230.00
Purchase #7	$141.53	11.146%	$157.3049	$157.30	$157.30	$157.30
7 purchase totals =	$949.41		$1,016.2980	$1,016.29	$1,016.35	$1,016.30