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	$174.66	8.540%	$189.576	$189.58	$189.60	$189.60
Purchase #2	$41.85	4.553%	$43.7554	$43.76	$43.75	$43.80
Purchase #3	$200.96	10.673%	$222.4085	$222.41	$222.40	$222.40
Purchase #4	$115.49	10.794%	$127.956	$127.96	$127.95	$128.00
Purchase #5	$122.85	5.865%	$130.0552	$130.06	$130.05	$130.10
Purchase #6	$161.84	12.781%	$182.5248	$182.52	$182.50	$182.50
Purchase #7	$223.82	8.763%	$243.4333	$243.43	$243.45	$243.40
7 purchase totals =	$1,041.47		$1,139.7092	$1,139.72	$1,139.70	$1,139.80