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	$8.62	3.726%	$8.9412	$8.94	$8.95	$8.90
Purchase #2	$44.55	13.504%	$50.566	$50.57	$50.55	$50.60
Purchase #3	$138.63	5.405%	$146.123	$146.12	$146.10	$146.10
Purchase #4	$157.27	3.463%	$162.7163	$162.72	$162.70	$162.70
Purchase #5	$128.63	11.730%	$143.7183	$143.72	$143.70	$143.70
Purchase #6	$247.58	3.354%	$255.8838	$255.88	$255.90	$255.90
Purchase #7	$8.31	3.335%	$8.5871	$8.59	$8.60	$8.60
7 purchase totals =	$733.59		$776.5357	$776.54	$776.50	$776.50