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	$112.84	6.218%	$119.8564	$119.86	$119.85	$119.90
Purchase #2	$21.56	4.775%	$22.5895	$22.59	$22.60	$22.60
Purchase #3	$92.42	13.236%	$104.6527	$104.65	$104.65	$104.70
Purchase #4	$79.61	12.852%	$89.8415	$89.84	$89.85	$89.80
Purchase #5	$21.89	11.823%	$24.4781	$24.48	$24.50	$24.50
Purchase #6	$166.44	3.756%	$172.6915	$172.69	$172.70	$172.70
Purchase #7	$239.37	8.625%	$260.0157	$260.02	$260.00	$260.00
7 purchase totals =	$734.13		$794.1254	$794.13	$794.15	$794.20