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	$43.91	12.771%	$49.5177	$49.52	$49.50	$49.50
Purchase #2	$99.47	12.346%	$111.7506	$111.75	$111.75	$111.80
Purchase #3	$13.95	12.302%	$15.6661	$15.67	$15.65	$15.70
Purchase #4	$16.83	13.816%	$19.1552	$19.16	$19.15	$19.20
Purchase #5	$7.97	11.250%	$8.8666	$8.87	$8.85	$8.90
Purchase #6	$37.42	12.688%	$42.1678	$42.17	$42.15	$42.20
Purchase #7	$122.67	6.131%	$130.1909	$130.19	$130.20	$130.20
7 purchase totals =	$342.22		$377.3149	$377.33	$377.25	$377.50