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	$196.60	13.506%	$223.1528	$223.15	$223.15	$223.20
Purchase #2	$99.27	6.243%	$105.4674	$105.47	$105.45	$105.50
Purchase #3	$33.66	9.280%	$36.7836	$36.78	$36.80	$36.80
Purchase #4	$20.25	9.762%	$22.2268	$22.23	$22.25	$22.20
Purchase #5	$151.43	12.147%	$169.8242	$169.82	$169.80	$169.80
Purchase #6	$246.48	12.433%	$277.1249	$277.12	$277.10	$277.10
Purchase #7	$54.47	7.222%	$58.4038	$58.40	$58.40	$58.40
7 purchase totals =	$802.16		$892.9835	$892.97	$892.95	$893.00