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	$169.46	7.851%	$182.7643	$182.76	$182.75	$182.80
Purchase #2	$14.66	12.838%	$16.5421	$16.54	$16.55	$16.50
Purchase #3	$213.25	4.842%	$223.5756	$223.58	$223.60	$223.60
Purchase #4	$44.33	11.253%	$49.3185	$49.32	$49.30	$49.30
Purchase #5	$59.76	4.114%	$62.2185	$62.22	$62.20	$62.20
Purchase #6	$61.28	7.748%	$66.028	$66.03	$66.05	$66.00
Purchase #7	$52.95	12.399%	$59.5153	$59.52	$59.50	$59.50
7 purchase totals =	$615.69		$659.9623	$659.97	$659.95	$659.90