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	$213.94	3.660%	$221.7702	$221.77	$221.75	$221.80
Purchase #2	$49.31	6.624%	$52.5763	$52.58	$52.60	$52.60
Purchase #3	$88.81	11.218%	$98.7727	$98.77	$98.75	$98.80
Purchase #4	$151.82	13.603%	$172.4721	$172.47	$172.45	$172.50
Purchase #5	$65.40	6.673%	$69.7641	$69.76	$69.75	$69.80
Purchase #6	$61.38	6.123%	$65.1383	$65.14	$65.15	$65.10
Purchase #7	$151.64	13.256%	$171.7414	$171.74	$171.75	$171.70
7 purchase totals =	$782.30		$852.2351	$852.23	$852.20	$852.30