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	$28.50	4.680%	$29.8338	$29.83	$29.85	$29.80
Purchase #2	$196.68	6.694%	$209.8458	$209.85	$209.85	$209.80
Purchase #3	$36.48	7.178%	$39.0985	$39.10	$39.10	$39.10
Purchase #4	$83.55	11.644%	$93.2786	$93.28	$93.30	$93.30
Purchase #5	$48.39	9.617%	$53.0437	$53.04	$53.05	$53.00
Purchase #6	$35.41	4.122%	$36.8696	$36.87	$36.85	$36.90
Purchase #7	$105.83	5.337%	$111.4781	$111.48	$111.50	$111.50
7 purchase totals =	$534.84		$573.4481	$573.45	$573.50	$573.40