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	$194.53	10.786%	$215.512	$215.51	$215.50	$215.50
Purchase #2	$195.63	13.135%	$221.326	$221.33	$221.35	$221.30
Purchase #3	$159.41	5.283%	$167.8316	$167.83	$167.85	$167.80
Purchase #4	$20.42	9.833%	$22.4279	$22.43	$22.45	$22.40
Purchase #5	$85.45	3.527%	$88.4638	$88.46	$88.45	$88.50
Purchase #6	$100.42	10.648%	$111.1127	$111.11	$111.10	$111.10
Purchase #7	$77.84	6.355%	$82.7867	$82.79	$82.80	$82.80
7 purchase totals =	$833.70		$909.4607	$909.46	$909.50	$909.40