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	$64.56	12.610%	$72.701	$72.70	$72.70	$72.70
Purchase #2	$117.49	12.334%	$131.9812	$131.98	$132.00	$132.00
Purchase #3	$61.72	11.157%	$68.6061	$68.61	$68.60	$68.60
Purchase #4	$122.51	6.534%	$130.5148	$130.51	$130.50	$130.50
Purchase #5	$56.36	5.393%	$59.3995	$59.40	$59.40	$59.40
Purchase #6	$69.77	4.802%	$73.1204	$73.12	$73.10	$73.10
Purchase #7	$182.87	9.527%	$200.292	$200.29	$200.30	$200.30
7 purchase totals =	$675.28		$736.6150	$736.61	$736.60	$736.60