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	$248.46	11.303%	$276.5434	$276.54	$276.55	$276.50
Purchase #2	$10.43	3.799%	$10.8262	$10.83	$10.85	$10.80
Purchase #3	$109.77	5.814%	$116.152	$116.15	$116.15	$116.20
Purchase #4	$35.32	12.796%	$39.8395	$39.84	$39.85	$39.80
Purchase #5	$54.42	9.461%	$59.5687	$59.57	$59.55	$59.60
Purchase #6	$83.32	6.735%	$88.9316	$88.93	$88.95	$88.90
Purchase #7	$119.62	4.109%	$124.5352	$124.54	$124.55	$124.50
7 purchase totals =	$661.34		$716.3966	$716.40	$716.45	$716.30