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	$204.49	9.674%	$224.2724	$224.27	$224.25	$224.30
Purchase #2	$214.51	6.596%	$228.6591	$228.66	$228.65	$228.70
Purchase #3	$207.46	13.124%	$234.6871	$234.69	$234.70	$234.70
Purchase #4	$178.77	5.327%	$188.2931	$188.29	$188.30	$188.30
Purchase #5	$193.42	11.240%	$215.1604	$215.16	$215.15	$215.20
Purchase #6	$53.89	13.725%	$61.2864	$61.29	$61.30	$61.30
Purchase #7	$139.79	5.807%	$147.9076	$147.91	$147.90	$147.90
7 purchase totals =	$1,192.33		$1,300.2661	$1,300.27	$1,300.25	$1,300.40