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	$98.37	13.131%	$111.287	$111.29	$111.30	$111.30
Purchase #2	$125.78	4.557%	$131.5118	$131.51	$131.50	$131.50
Purchase #3	$149.59	13.557%	$169.8699	$169.87	$169.85	$169.90
Purchase #4	$240.73	6.315%	$255.9321	$255.93	$255.95	$255.90
Purchase #5	$55.71	8.177%	$60.2654	$60.27	$60.25	$60.30
Purchase #6	$51.85	6.619%	$55.282	$55.28	$55.30	$55.30
Purchase #7	$239.71	9.436%	$262.329	$262.33	$262.35	$262.30
7 purchase totals =	$961.74		$1,046.4772	$1,046.48	$1,046.50	$1,046.50