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	$116.41	9.470%	$127.434	$127.43	$127.45	$127.40
Purchase #2	$162.30	6.261%	$172.4616	$172.46	$172.45	$172.50
Purchase #3	$186.80	10.874%	$207.1126	$207.11	$207.10	$207.10
Purchase #4	$83.57	8.306%	$90.5113	$90.51	$90.50	$90.50
Purchase #5	$5.87	11.281%	$6.5322	$6.53	$6.55	$6.50
Purchase #6	$228.40	8.365%	$247.5057	$247.51	$247.50	$247.50
Purchase #7	$220.40	12.127%	$247.1279	$247.13	$247.15	$247.10
7 purchase totals =	$1,003.75		$1,098.6853	$1,098.68	$1,098.70	$1,098.60