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	$86.72	7.424%	$93.1581	$93.16	$93.15	$93.20
Purchase #2	$219.33	6.667%	$233.9527	$233.95	$233.95	$234.00
Purchase #3	$138.41	5.741%	$146.3561	$146.36	$146.35	$146.40
Purchase #4	$169.38	9.590%	$185.6235	$185.62	$185.60	$185.60
Purchase #5	$232.98	9.550%	$255.2296	$255.23	$255.25	$255.20
Purchase #6	$160.41	6.125%	$170.2351	$170.24	$170.25	$170.20
Purchase #7	$54.47	4.219%	$56.7681	$56.77	$56.75	$56.80
7 purchase totals =	$1,061.70		$1,141.3232	$1,141.33	$1,141.30	$1,141.40