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	$97.28	7.261%	$104.3435	$104.34	$104.35	$104.30
Purchase #2	$194.72	10.720%	$215.594	$215.59	$215.60	$215.60
Purchase #3	$70.55	11.786%	$78.865	$78.87	$78.85	$78.90
Purchase #4	$100.82	8.235%	$109.1225	$109.12	$109.10	$109.10
Purchase #5	$233.41	7.278%	$250.3976	$250.40	$250.40	$250.40
Purchase #6	$144.68	8.252%	$156.619	$156.62	$156.60	$156.60
Purchase #7	$35.52	13.760%	$40.4076	$40.41	$40.40	$40.40
7 purchase totals =	$876.98		$955.3492	$955.35	$955.30	$955.30