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	$82.53	4.212%	$86.0062	$86.01	$86.00	$86.00
Purchase #2	$159.54	13.175%	$180.5594	$180.56	$180.55	$180.60
Purchase #3	$37.36	10.167%	$41.1584	$41.16	$41.15	$41.20
Purchase #4	$89.56	4.117%	$93.2472	$93.25	$93.25	$93.20
Purchase #5	$35.43	9.377%	$38.7523	$38.75	$38.75	$38.80
Purchase #6	$75.50	12.654%	$85.0538	$85.05	$85.05	$85.10
Purchase #7	$83.78	8.267%	$90.7061	$90.71	$90.70	$90.70
7 purchase totals =	$563.70		$615.4834	$615.49	$615.45	$615.60