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	$153.97	13.717%	$175.0901	$175.09	$175.10	$175.10
Purchase #2	$110.41	13.472%	$125.2844	$125.28	$125.30	$125.30
Purchase #3	$214.41	3.292%	$221.4684	$221.47	$221.45	$221.50
Purchase #4	$102.85	8.113%	$111.1942	$111.19	$111.20	$111.20
Purchase #5	$80.98	12.774%	$91.3244	$91.32	$91.30	$91.30
Purchase #6	$108.72	7.165%	$116.5098	$116.51	$116.50	$116.50
Purchase #7	$73.51	13.421%	$83.3758	$83.38	$83.40	$83.40
7 purchase totals =	$844.85		$924.2471	$924.24	$924.25	$924.30