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	$40.68	6.156%	$43.1843	$43.18	$43.20	$43.20
Purchase #2	$184.32	13.316%	$208.8641	$208.86	$208.85	$208.90
Purchase #3	$173.69	10.289%	$191.561	$191.56	$191.55	$191.60
Purchase #4	$236.66	4.754%	$247.9108	$247.91	$247.90	$247.90
Purchase #5	$248.92	10.507%	$275.074	$275.07	$275.05	$275.10
Purchase #6	$147.45	11.517%	$164.4318	$164.43	$164.45	$164.40
Purchase #7	$190.83	11.228%	$212.2564	$212.26	$212.25	$212.30
7 purchase totals =	$1,222.55		$1,343.2824	$1,343.27	$1,343.25	$1,343.40