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	$148.27	11.555%	$165.4026	$165.40	$165.40	$165.40
Purchase #2	$202.82	4.324%	$211.5899	$211.59	$211.60	$211.60
Purchase #3	$247.93	4.304%	$258.6009	$258.60	$258.60	$258.60
Purchase #4	$213.30	8.652%	$231.7547	$231.75	$231.75	$231.80
Purchase #5	$8.34	6.602%	$8.8906	$8.89	$8.90	$8.90
Purchase #6	$82.67	9.728%	$90.7121	$90.71	$90.70	$90.70
Purchase #7	$230.39	8.778%	$250.6136	$250.61	$250.60	$250.60
7 purchase totals =	$1,133.72		$1,217.5644	$1,217.55	$1,217.55	$1,217.60