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	$175.76	13.201%	$198.9621	$198.96	$198.95	$199.00
Purchase #2	$22.55	13.707%	$25.6409	$25.64	$25.65	$25.60
Purchase #3	$234.50	12.357%	$263.4772	$263.48	$263.50	$263.50
Purchase #4	$143.31	5.146%	$150.6847	$150.68	$150.70	$150.70
Purchase #5	$84.48	13.275%	$95.6947	$95.69	$95.70	$95.70
Purchase #6	$104.78	6.719%	$111.8202	$111.82	$111.80	$111.80
Purchase #7	$76.69	7.153%	$82.1756	$82.18	$82.20	$82.20
7 purchase totals =	$842.07		$928.4554	$928.45	$928.50	$928.50