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	$130.40	7.709%	$140.4525	$140.45	$140.45	$140.50
Purchase #2	$93.93	11.693%	$104.9132	$104.91	$104.90	$104.90
Purchase #3	$76.29	13.534%	$86.6151	$86.62	$86.60	$86.60
Purchase #4	$59.93	10.498%	$66.2215	$66.22	$66.20	$66.20
Purchase #5	$160.30	3.346%	$165.6636	$165.66	$165.65	$165.70
Purchase #6	$194.89	7.267%	$209.0527	$209.05	$209.05	$209.10
Purchase #7	$102.78	11.369%	$114.4651	$114.47	$114.45	$114.50
7 purchase totals =	$818.52		$887.3837	$887.38	$887.30	$887.50