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	$152.67	13.340%	$173.0362	$173.04	$173.05	$173.00
Purchase #2	$165.66	3.796%	$171.9485	$171.95	$171.95	$171.90
Purchase #3	$173.42	8.729%	$188.5578	$188.56	$188.55	$188.60
Purchase #4	$62.67	5.670%	$66.2234	$66.22	$66.20	$66.20
Purchase #5	$208.81	9.355%	$228.3442	$228.34	$228.35	$228.30
Purchase #6	$55.50	11.572%	$61.9225	$61.92	$61.90	$61.90
Purchase #7	$236.83	13.746%	$269.3847	$269.38	$269.40	$269.40
7 purchase totals =	$1,055.56		$1,159.4173	$1,159.41	$1,159.40	$1,159.30