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	$232.82	7.468%	$250.207	$250.21	$250.20	$250.20
Purchase #2	$114.70	10.755%	$127.036	$127.04	$127.05	$127.00
Purchase #3	$152.97	7.514%	$164.4642	$164.46	$164.45	$164.50
Purchase #4	$20.97	5.393%	$22.1009	$22.10	$22.10	$22.10
Purchase #5	$144.70	13.557%	$164.317	$164.32	$164.30	$164.30
Purchase #6	$74.84	10.552%	$82.7371	$82.74	$82.75	$82.70
Purchase #7	$19.54	3.825%	$20.2874	$20.29	$20.30	$20.30
7 purchase totals =	$760.54		$831.1496	$831.16	$831.15	$831.10