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	$95.84	6.192%	$101.7744	$101.77	$101.75	$101.80
Purchase #2	$86.32	5.111%	$90.7318	$90.73	$90.75	$90.70
Purchase #3	$187.29	12.860%	$211.3755	$211.38	$211.40	$211.40
Purchase #4	$69.68	4.186%	$72.5968	$72.60	$72.60	$72.60
Purchase #5	$27.44	8.858%	$29.8706	$29.87	$29.85	$29.90
Purchase #6	$195.38	4.459%	$204.092	$204.09	$204.10	$204.10
Purchase #7	$10.57	3.558%	$10.9461	$10.95	$10.95	$10.90
7 purchase totals =	$672.52		$721.3872	$721.39	$721.40	$721.40