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	$141.35	7.279%	$151.6389	$151.64	$151.65	$151.60
Purchase #2	$245.48	7.735%	$264.4679	$264.47	$264.45	$264.50
Purchase #3	$247.68	6.112%	$262.8182	$262.82	$262.80	$262.80
Purchase #4	$52.35	3.367%	$54.1126	$54.11	$54.10	$54.10
Purchase #5	$17.77	8.651%	$19.3073	$19.31	$19.30	$19.30
Purchase #6	$103.51	10.803%	$114.6922	$114.69	$114.70	$114.70
Purchase #7	$92.67	7.395%	$99.5229	$99.52	$99.50	$99.50
7 purchase totals =	$900.81		$966.5600	$966.56	$966.50	$966.50