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	$103.50	10.259%	$114.1181	$114.12	$114.10	$114.10
Purchase #2	$246.53	7.286%	$264.4922	$264.49	$264.50	$264.50
Purchase #3	$52.45	12.772%	$59.1489	$59.15	$59.15	$59.10
Purchase #4	$46.58	3.734%	$48.3193	$48.32	$48.30	$48.30
Purchase #5	$207.80	12.872%	$234.548	$234.55	$234.55	$234.50
Purchase #6	$248.79	10.273%	$274.3482	$274.35	$274.35	$274.30
Purchase #7	$65.69	6.114%	$69.7063	$69.71	$69.70	$69.70
7 purchase totals =	$971.34		$1,064.6810	$1,064.69	$1,064.65	$1,064.50