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	$141.41	10.240%	$155.8904	$155.89	$155.90	$155.90
Purchase #2	$17.82	9.492%	$19.5115	$19.51	$19.50	$19.50
Purchase #3	$243.73	8.249%	$263.8353	$263.84	$263.85	$263.80
Purchase #4	$54.52	9.822%	$59.875	$59.88	$59.90	$59.90
Purchase #5	$67.74	9.627%	$74.2613	$74.26	$74.25	$74.30
Purchase #6	$38.30	3.739%	$39.732	$39.73	$39.75	$39.70
Purchase #7	$85.42	11.350%	$95.1152	$95.12	$95.10	$95.10
7 purchase totals =	$648.94		$708.2207	$708.23	$708.25	$708.20