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	$134.71	12.551%	$151.6175	$151.62	$151.60	$151.60
Purchase #2	$148.43	5.321%	$156.328	$156.33	$156.35	$156.30
Purchase #3	$149.35	12.583%	$168.1427	$168.14	$168.15	$168.10
Purchase #4	$247.70	12.225%	$277.9813	$277.98	$278.00	$278.00
Purchase #5	$54.38	5.543%	$57.3943	$57.39	$57.40	$57.40
Purchase #6	$151.28	13.109%	$171.1113	$171.11	$171.10	$171.10
Purchase #7	$151.45	3.862%	$157.299	$157.30	$157.30	$157.30
7 purchase totals =	$1,037.30		$1,139.8741	$1,139.87	$1,139.90	$1,139.80