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	$229.87	10.329%	$253.6133	$253.61	$253.60	$253.60
Purchase #2	$159.72	6.809%	$170.5953	$170.60	$170.60	$170.60
Purchase #3	$68.50	5.788%	$72.4648	$72.46	$72.45	$72.50
Purchase #4	$93.94	12.209%	$105.4091	$105.41	$105.40	$105.40
Purchase #5	$246.96	10.493%	$272.8735	$272.87	$272.85	$272.90
Purchase #6	$209.37	6.582%	$223.1507	$223.15	$223.15	$223.20
Purchase #7	$169.80	6.181%	$180.2953	$180.30	$180.30	$180.30
7 purchase totals =	$1,178.16		$1,278.4020	$1,278.40	$1,278.35	$1,278.50