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	$32.26	9.567%	$35.3463	$35.35	$35.35	$35.30
Purchase #2	$149.34	5.774%	$157.9629	$157.96	$157.95	$158.00
Purchase #3	$53.40	5.398%	$56.2825	$56.28	$56.30	$56.30
Purchase #4	$111.87	4.435%	$116.8314	$116.83	$116.85	$116.80
Purchase #5	$170.89	8.571%	$185.537	$185.54	$185.55	$185.50
Purchase #6	$165.52	11.110%	$183.9093	$183.91	$183.90	$183.90
Purchase #7	$21.51	13.741%	$24.4657	$24.47	$24.45	$24.50
7 purchase totals =	$704.79		$760.3351	$760.34	$760.35	$760.30