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	$149.59	8.169%	$161.81	$161.81	$161.80	$161.80
Purchase #2	$145.95	5.864%	$154.5085	$154.51	$154.50	$154.50
Purchase #3	$188.86	4.191%	$196.7751	$196.78	$196.80	$196.80
Purchase #4	$43.82	3.472%	$45.3414	$45.34	$45.35	$45.30
Purchase #5	$50.81	12.422%	$57.1216	$57.12	$57.10	$57.10
Purchase #6	$198.80	5.361%	$209.4577	$209.46	$209.45	$209.50
Purchase #7	$241.48	8.814%	$262.764	$262.76	$262.75	$262.80
7 purchase totals =	$1,019.31		$1,087.7783	$1,087.78	$1,087.75	$1,087.80