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	$245.61	13.365%	$278.4358	$278.44	$278.45	$278.40
Purchase #2	$247.78	3.228%	$255.7783	$255.78	$255.80	$255.80
Purchase #3	$215.54	6.275%	$229.0651	$229.07	$229.05	$229.10
Purchase #4	$74.67	9.249%	$81.5762	$81.58	$81.60	$81.60
Purchase #5	$10.29	4.360%	$10.7386	$10.74	$10.75	$10.70
Purchase #6	$201.55	10.780%	$223.2771	$223.28	$223.30	$223.30
Purchase #7	$151.37	4.767%	$158.5858	$158.59	$158.60	$158.60
7 purchase totals =	$1,146.81		$1,237.4569	$1,237.48	$1,237.55	$1,237.50