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	$152.42	4.640%	$159.4923	$159.49	$159.50	$159.50
Purchase #2	$140.64	7.784%	$151.5874	$151.59	$151.60	$151.60
Purchase #3	$107.91	9.536%	$118.2003	$118.20	$118.20	$118.20
Purchase #4	$92.72	3.265%	$95.7473	$95.75	$95.75	$95.70
Purchase #5	$95.73	13.753%	$108.8957	$108.90	$108.90	$108.90
Purchase #6	$159.73	7.113%	$171.0916	$171.09	$171.10	$171.10
Purchase #7	$218.72	4.214%	$227.9369	$227.94	$227.95	$227.90
7 purchase totals =	$967.87		$1,032.9515	$1,032.96	$1,033.00	$1,032.90