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	$112.25	3.451%	$116.1237	$116.12	$116.10	$116.10
Purchase #2	$92.51	4.155%	$96.3538	$96.35	$96.35	$96.40
Purchase #3	$78.95	13.139%	$89.3232	$89.32	$89.30	$89.30
Purchase #4	$22.62	12.819%	$25.5197	$25.52	$25.50	$25.50
Purchase #5	$149.75	9.854%	$164.5064	$164.51	$164.50	$164.50
Purchase #6	$170.61	11.693%	$190.5594	$190.56	$190.55	$190.60
Purchase #7	$165.37	6.386%	$175.9305	$175.93	$175.95	$175.90
7 purchase totals =	$792.06		$858.3167	$858.31	$858.25	$858.30