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	$41.37	9.706%	$45.3854	$45.39	$45.40	$45.40
Purchase #2	$135.63	11.684%	$151.477	$151.48	$151.50	$151.50
Purchase #3	$87.99	7.805%	$94.8576	$94.86	$94.85	$94.90
Purchase #4	$14.25	8.540%	$15.467	$15.47	$15.45	$15.50
Purchase #5	$94.60	11.560%	$105.5358	$105.54	$105.55	$105.50
Purchase #6	$194.59	7.203%	$208.6063	$208.61	$208.60	$208.60
Purchase #7	$233.52	8.518%	$253.4112	$253.41	$253.40	$253.40
7 purchase totals =	$801.95		$874.7403	$874.76	$874.75	$874.80