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	$108.78	8.738%	$118.2852	$118.29	$118.30	$118.30
Purchase #2	$183.33	13.735%	$208.5104	$208.51	$208.50	$208.50
Purchase #3	$229.98	13.321%	$260.6156	$260.62	$260.60	$260.60
Purchase #4	$157.82	4.574%	$165.0387	$165.04	$165.05	$165.00
Purchase #5	$20.26	11.343%	$22.5581	$22.56	$22.55	$22.60
Purchase #6	$78.50	13.303%	$88.9429	$88.94	$88.95	$88.90
Purchase #7	$218.39	6.183%	$231.8931	$231.89	$231.90	$231.90
7 purchase totals =	$997.06		$1,095.8440	$1,095.85	$1,095.85	$1,095.80