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	$137.36	10.573%	$151.8831	$151.88	$151.90	$151.90
Purchase #2	$102.86	7.729%	$110.81	$110.81	$110.80	$110.80
Purchase #3	$230.28	10.275%	$253.9413	$253.94	$253.95	$253.90
Purchase #4	$202.88	11.860%	$226.9416	$226.94	$226.95	$226.90
Purchase #5	$216.48	12.411%	$243.3473	$243.35	$243.35	$243.30
Purchase #6	$111.72	10.650%	$123.6182	$123.62	$123.60	$123.60
Purchase #7	$66.88	11.560%	$74.6113	$74.61	$74.60	$74.60
7 purchase totals =	$1,068.46		$1,185.1528	$1,185.15	$1,185.15	$1,185.00