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	$146.64	4.755%	$153.6127	$153.61	$153.60	$153.60
Purchase #2	$160.27	7.170%	$171.7614	$171.76	$171.75	$171.80
Purchase #3	$53.44	11.574%	$59.6251	$59.63	$59.65	$59.60
Purchase #4	$19.56	3.519%	$20.2483	$20.25	$20.25	$20.20
Purchase #5	$38.51	3.376%	$39.8101	$39.81	$39.80	$39.80
Purchase #6	$62.52	8.110%	$67.5904	$67.59	$67.60	$67.60
Purchase #7	$72.95	5.303%	$76.8185	$76.82	$76.80	$76.80
7 purchase totals =	$553.89		$589.4665	$589.47	$589.45	$589.40