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	$198.25	7.282%	$212.6866	$212.69	$212.70	$212.70
Purchase #2	$19.40	5.261%	$20.4206	$20.42	$20.40	$20.40
Purchase #3	$192.73	3.300%	$199.0901	$199.09	$199.10	$199.10
Purchase #4	$102.83	8.311%	$111.3762	$111.38	$111.40	$111.40
Purchase #5	$155.45	10.462%	$171.7132	$171.71	$171.70	$171.70
Purchase #6	$50.72	10.502%	$56.0466	$56.05	$56.05	$56.00
Purchase #7	$68.51	13.849%	$77.9979	$78.00	$78.00	$78.00
7 purchase totals =	$787.89		$849.3312	$849.34	$849.35	$849.30