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	$159.50	6.492%	$169.8547	$169.85	$169.85	$169.90
Purchase #2	$66.71	5.530%	$70.3991	$70.40	$70.40	$70.40
Purchase #3	$104.48	6.768%	$111.5512	$111.55	$111.55	$111.60
Purchase #4	$55.43	3.203%	$57.2054	$57.21	$57.20	$57.20
Purchase #5	$241.91	7.439%	$259.9057	$259.91	$259.90	$259.90
Purchase #6	$37.64	4.393%	$39.2935	$39.29	$39.30	$39.30
Purchase #7	$92.80	7.761%	$100.0022	$100.00	$100.00	$100.00
7 purchase totals =	$758.47		$808.2118	$808.21	$808.20	$808.30