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	$82.95	7.500%	$89.1713	$89.17	$89.15	$89.20
Purchase #2	$18.94	8.483%	$20.5467	$20.55	$20.55	$20.50
Purchase #3	$147.60	13.695%	$167.8138	$167.81	$167.80	$167.80
Purchase #4	$212.67	6.748%	$227.021	$227.02	$227.00	$227.00
Purchase #5	$193.52	6.177%	$205.4737	$205.47	$205.45	$205.50
Purchase #6	$136.47	13.312%	$154.6369	$154.64	$154.65	$154.60
Purchase #7	$202.52	11.219%	$225.2407	$225.24	$225.25	$225.20
7 purchase totals =	$994.67		$1,089.9041	$1,089.90	$1,089.85	$1,089.80