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	$146.51	4.449%	$153.0282	$153.03	$153.05	$153.00
Purchase #2	$48.59	4.556%	$50.8038	$50.80	$50.80	$50.80
Purchase #3	$245.47	7.801%	$264.6191	$264.62	$264.60	$264.60
Purchase #4	$238.54	10.604%	$263.8348	$263.83	$263.85	$263.80
Purchase #5	$43.66	3.710%	$45.2798	$45.28	$45.30	$45.30
Purchase #6	$78.85	9.407%	$86.2674	$86.27	$86.25	$86.30
Purchase #7	$149.90	4.789%	$157.0787	$157.08	$157.10	$157.10
7 purchase totals =	$951.52		$1,020.9118	$1,020.91	$1,020.95	$1,020.90