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	$222.80	9.794%	$244.621	$244.62	$244.60	$244.60
Purchase #2	$6.44	11.388%	$7.1734	$7.17	$7.15	$7.20
Purchase #3	$179.27	11.787%	$200.4006	$200.40	$200.40	$200.40
Purchase #4	$41.70	9.782%	$45.7791	$45.78	$45.80	$45.80
Purchase #5	$54.55	13.753%	$62.0523	$62.05	$62.05	$62.10
Purchase #6	$238.69	6.177%	$253.4339	$253.43	$253.45	$253.40
Purchase #7	$146.56	8.449%	$158.9429	$158.94	$158.95	$158.90
7 purchase totals =	$890.01		$972.4032	$972.39	$972.40	$972.40