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	$130.73	5.479%	$137.8927	$137.89	$137.90	$137.90
Purchase #2	$80.54	8.439%	$87.3368	$87.34	$87.35	$87.30
Purchase #3	$52.64	8.322%	$57.0207	$57.02	$57.00	$57.00
Purchase #4	$16.74	3.580%	$17.3393	$17.34	$17.35	$17.30
Purchase #5	$35.54	13.259%	$40.2522	$40.25	$40.25	$40.30
Purchase #6	$98.69	12.866%	$111.3875	$111.39	$111.40	$111.40
Purchase #7	$154.84	4.273%	$161.4563	$161.46	$161.45	$161.50
7 purchase totals =	$569.72		$612.6855	$612.69	$612.70	$612.70