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	$158.64	4.606%	$165.947	$165.95	$165.95	$165.90
Purchase #2	$239.74	6.583%	$255.5221	$255.52	$255.50	$255.50
Purchase #3	$135.51	9.592%	$148.5081	$148.51	$148.50	$148.50
Purchase #4	$118.95	9.843%	$130.6582	$130.66	$130.65	$130.70
Purchase #5	$19.84	10.420%	$21.9073	$21.91	$21.90	$21.90
Purchase #6	$232.60	13.665%	$264.3848	$264.38	$264.40	$264.40
Purchase #7	$66.53	9.181%	$72.6381	$72.64	$72.65	$72.60
7 purchase totals =	$971.81		$1,059.5656	$1,059.57	$1,059.55	$1,059.50