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	$143.28	11.868%	$160.2845	$160.28	$160.30	$160.30
Purchase #2	$30.37	6.799%	$32.4349	$32.43	$32.45	$32.40
Purchase #3	$65.72	11.388%	$73.2042	$73.20	$73.20	$73.20
Purchase #4	$85.72	11.530%	$95.6035	$95.60	$95.60	$95.60
Purchase #5	$160.86	8.851%	$175.0977	$175.10	$175.10	$175.10
Purchase #6	$63.99	13.694%	$72.7528	$72.75	$72.75	$72.80
Purchase #7	$73.48	13.824%	$83.6379	$83.64	$83.65	$83.60
7 purchase totals =	$623.42		$693.0155	$693.00	$693.05	$693.00