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	$90.44	4.338%	$94.3633	$94.36	$94.35	$94.40
Purchase #2	$173.30	9.473%	$189.7167	$189.72	$189.70	$189.70
Purchase #3	$166.93	3.203%	$172.2768	$172.28	$172.30	$172.30
Purchase #4	$119.54	10.555%	$132.1574	$132.16	$132.15	$132.20
Purchase #5	$235.92	8.791%	$256.6597	$256.66	$256.65	$256.70
Purchase #6	$82.81	4.320%	$86.3874	$86.39	$86.40	$86.40
Purchase #7	$32.89	12.785%	$37.095	$37.10	$37.10	$37.10
7 purchase totals =	$901.83		$968.6563	$968.67	$968.65	$968.80