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	$43.49	11.108%	$48.3209	$48.32	$48.30	$48.30
Purchase #2	$29.62	9.589%	$32.4603	$32.46	$32.45	$32.50
Purchase #3	$85.50	6.558%	$91.1071	$91.11	$91.10	$91.10
Purchase #4	$94.95	5.460%	$100.1343	$100.13	$100.15	$100.10
Purchase #5	$19.54	3.362%	$20.1969	$20.20	$20.20	$20.20
Purchase #6	$195.76	11.632%	$218.5308	$218.53	$218.55	$218.50
Purchase #7	$53.29	6.313%	$56.6542	$56.65	$56.65	$56.70
7 purchase totals =	$522.15		$567.4045	$567.40	$567.40	$567.40