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	$124.93	4.786%	$130.9091	$130.91	$130.90	$130.90
Purchase #2	$68.78	4.543%	$71.9047	$71.90	$71.90	$71.90
Purchase #3	$208.94	3.734%	$216.7418	$216.74	$216.75	$216.70
Purchase #4	$19.85	7.103%	$21.2599	$21.26	$21.25	$21.30
Purchase #5	$189.26	11.209%	$210.4742	$210.47	$210.45	$210.50
Purchase #6	$29.45	10.838%	$32.6418	$32.64	$32.65	$32.60
Purchase #7	$127.61	11.172%	$141.8666	$141.87	$141.85	$141.90
7 purchase totals =	$768.82		$825.7981	$825.79	$825.75	$825.80