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	$200.78	11.152%	$223.171	$223.17	$223.15	$223.20
Purchase #2	$84.91	6.523%	$90.4487	$90.45	$90.45	$90.40
Purchase #3	$181.34	10.404%	$200.2066	$200.21	$200.20	$200.20
Purchase #4	$143.39	12.577%	$161.4242	$161.42	$161.40	$161.40
Purchase #5	$112.28	4.778%	$117.6447	$117.64	$117.65	$117.60
Purchase #6	$169.96	12.696%	$191.5381	$191.54	$191.55	$191.50
Purchase #7	$170.29	12.607%	$191.7585	$191.76	$191.75	$191.80
7 purchase totals =	$1,062.95		$1,176.1918	$1,176.19	$1,176.15	$1,176.10