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	$211.65	6.555%	$225.5237	$225.52	$225.50	$225.50
Purchase #2	$42.70	4.618%	$44.6719	$44.67	$44.65	$44.70
Purchase #3	$69.64	10.282%	$76.8004	$76.80	$76.80	$76.80
Purchase #4	$123.94	6.798%	$132.3654	$132.37	$132.35	$132.40
Purchase #5	$60.79	7.867%	$65.5723	$65.57	$65.55	$65.60
Purchase #6	$42.55	6.517%	$45.323	$45.32	$45.30	$45.30
Purchase #7	$159.49	3.853%	$165.6351	$165.64	$165.65	$165.60
7 purchase totals =	$710.76		$755.8918	$755.89	$755.80	$755.90