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	$60.34	7.177%	$64.6706	$64.67	$64.65	$64.70
Purchase #2	$185.90	6.796%	$198.5338	$198.53	$198.55	$198.50
Purchase #3	$77.70	7.376%	$83.4312	$83.43	$83.45	$83.40
Purchase #4	$240.70	6.147%	$255.4958	$255.50	$255.50	$255.50
Purchase #5	$146.33	3.601%	$151.5993	$151.60	$151.60	$151.60
Purchase #6	$198.26	3.459%	$205.1178	$205.12	$205.10	$205.10
Purchase #7	$155.48	10.266%	$171.4416	$171.44	$171.45	$171.40
7 purchase totals =	$1,064.71		$1,130.2901	$1,130.29	$1,130.30	$1,130.20