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	$145.70	11.666%	$162.6974	$162.70	$162.70	$162.70
Purchase #2	$218.53	10.625%	$241.7488	$241.75	$241.75	$241.70
Purchase #3	$17.82	3.282%	$18.4049	$18.40	$18.40	$18.40
Purchase #4	$55.46	7.601%	$59.6755	$59.68	$59.70	$59.70
Purchase #5	$158.41	6.492%	$168.694	$168.69	$168.70	$168.70
Purchase #6	$80.82	5.867%	$85.5617	$85.56	$85.55	$85.60
Purchase #7	$217.68	10.103%	$239.6722	$239.67	$239.65	$239.70
7 purchase totals =	$894.42		$976.4545	$976.45	$976.45	$976.50