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	$94.89	11.129%	$105.4503	$105.45	$105.45	$105.50
Purchase #2	$119.86	9.402%	$131.1292	$131.13	$131.15	$131.10
Purchase #3	$65.28	13.743%	$74.2514	$74.25	$74.25	$74.30
Purchase #4	$114.70	4.568%	$119.9395	$119.94	$119.95	$119.90
Purchase #5	$19.41	7.588%	$20.8828	$20.88	$20.90	$20.90
Purchase #6	$247.65	8.640%	$269.047	$269.05	$269.05	$269.00
Purchase #7	$65.37	4.694%	$68.4385	$68.44	$68.45	$68.40
7 purchase totals =	$727.16		$789.1387	$789.14	$789.20	$789.10