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	$176.62	4.646%	$184.8258	$184.83	$184.85	$184.80
Purchase #2	$90.72	3.561%	$93.9505	$93.95	$93.95	$94.00
Purchase #3	$129.79	3.225%	$133.9757	$133.98	$134.00	$134.00
Purchase #4	$44.98	9.233%	$49.133	$49.13	$49.15	$49.10
Purchase #5	$46.89	12.845%	$52.913	$52.91	$52.90	$52.90
Purchase #6	$29.89	4.176%	$31.1382	$31.14	$31.15	$31.10
Purchase #7	$33.46	7.251%	$35.8862	$35.89	$35.90	$35.90
7 purchase totals =	$552.35		$581.8224	$581.83	$581.90	$581.80