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	$31.80	12.476%	$35.7674	$35.77	$35.75	$35.80
Purchase #2	$216.84	3.191%	$223.7594	$223.76	$223.75	$223.80
Purchase #3	$35.90	4.726%	$37.5966	$37.60	$37.60	$37.60
Purchase #4	$120.89	12.617%	$136.1427	$136.14	$136.15	$136.10
Purchase #5	$97.75	10.823%	$108.3295	$108.33	$108.35	$108.30
Purchase #6	$134.29	5.143%	$141.1965	$141.20	$141.20	$141.20
Purchase #7	$123.35	7.493%	$132.5926	$132.59	$132.60	$132.60
7 purchase totals =	$760.82		$815.3847	$815.39	$815.40	$815.40