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	$71.88	9.668%	$78.8294	$78.83	$78.85	$78.80
Purchase #2	$110.30	7.191%	$118.2317	$118.23	$118.25	$118.20
Purchase #3	$99.79	10.534%	$110.3019	$110.30	$110.30	$110.30
Purchase #4	$192.72	13.849%	$219.4098	$219.41	$219.40	$219.40
Purchase #5	$32.78	10.864%	$36.3412	$36.34	$36.35	$36.30
Purchase #6	$62.45	4.431%	$65.2172	$65.22	$65.20	$65.20
Purchase #7	$95.36	4.243%	$99.4061	$99.41	$99.40	$99.40
7 purchase totals =	$665.28		$727.7373	$727.74	$727.75	$727.60