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	$182.42	3.472%	$188.7536	$188.75	$188.75	$188.80
Purchase #2	$243.46	7.164%	$260.9015	$260.90	$260.90	$260.90
Purchase #3	$26.97	6.225%	$28.6489	$28.65	$28.65	$28.60
Purchase #4	$70.49	11.342%	$78.485	$78.49	$78.50	$78.50
Purchase #5	$192.89	12.641%	$217.2732	$217.27	$217.25	$217.30
Purchase #6	$127.25	12.626%	$143.3166	$143.32	$143.30	$143.30
Purchase #7	$70.77	8.454%	$76.7529	$76.75	$76.75	$76.80
7 purchase totals =	$914.25		$994.1317	$994.13	$994.10	$994.20