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	$172.50	10.751%	$191.0455	$191.05	$191.05	$191.00
Purchase #2	$179.91	12.448%	$202.3052	$202.31	$202.30	$202.30
Purchase #3	$97.53	7.363%	$104.7111	$104.71	$104.70	$104.70
Purchase #4	$61.81	8.797%	$67.2474	$67.25	$67.25	$67.20
Purchase #5	$57.79	4.704%	$60.5084	$60.51	$60.50	$60.50
Purchase #6	$124.83	12.820%	$140.8332	$140.83	$140.85	$140.80
Purchase #7	$179.25	9.700%	$196.6373	$196.64	$196.65	$196.60
7 purchase totals =	$873.62		$963.2881	$963.30	$963.30	$963.10