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	$157.35	4.485%	$164.4071	$164.41	$164.40	$164.40
Purchase #2	$63.70	10.359%	$70.2987	$70.30	$70.30	$70.30
Purchase #3	$248.76	11.688%	$277.8351	$277.84	$277.85	$277.80
Purchase #4	$8.65	9.278%	$9.4525	$9.45	$9.45	$9.50
Purchase #5	$19.64	4.222%	$20.4692	$20.47	$20.45	$20.50
Purchase #6	$71.96	8.853%	$78.3306	$78.33	$78.35	$78.30
Purchase #7	$182.58	7.447%	$196.1767	$196.18	$196.20	$196.20
7 purchase totals =	$752.64		$816.9699	$816.98	$817.00	$817.00