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	$192.56	13.533%	$218.6191	$218.62	$218.60	$218.60
Purchase #2	$211.48	11.528%	$235.8594	$235.86	$235.85	$235.90
Purchase #3	$90.45	4.311%	$94.3493	$94.35	$94.35	$94.30
Purchase #4	$47.84	10.307%	$52.7709	$52.77	$52.75	$52.80
Purchase #5	$207.94	11.222%	$231.275	$231.28	$231.30	$231.30
Purchase #6	$166.30	3.166%	$171.5651	$171.57	$171.55	$171.60
Purchase #7	$130.33	10.139%	$143.5442	$143.54	$143.55	$143.50
7 purchase totals =	$1,046.90		$1,147.9830	$1,147.99	$1,147.95	$1,148.00