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	$69.78	4.232%	$72.7331	$72.73	$72.75	$72.70
Purchase #2	$123.41	7.347%	$132.4769	$132.48	$132.50	$132.50
Purchase #3	$203.97	11.545%	$227.5183	$227.52	$227.50	$227.50
Purchase #4	$30.90	7.511%	$33.2209	$33.22	$33.20	$33.20
Purchase #5	$87.72	4.556%	$91.7165	$91.72	$91.70	$91.70
Purchase #6	$52.97	12.429%	$59.5536	$59.55	$59.55	$59.60
Purchase #7	$233.65	12.358%	$262.5245	$262.52	$262.50	$262.50
7 purchase totals =	$802.40		$879.7438	$879.74	$879.70	$879.70