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	$211.66	6.450%	$225.3121	$225.31	$225.30	$225.30
Purchase #2	$227.65	11.272%	$253.3107	$253.31	$253.30	$253.30
Purchase #3	$68.87	4.851%	$72.2109	$72.21	$72.20	$72.20
Purchase #4	$148.62	6.549%	$158.3531	$158.35	$158.35	$158.40
Purchase #5	$96.65	9.526%	$105.8569	$105.86	$105.85	$105.90
Purchase #6	$219.71	10.368%	$242.4895	$242.49	$242.50	$242.50
Purchase #7	$125.88	4.131%	$131.0801	$131.08	$131.10	$131.10
7 purchase totals =	$1,099.04		$1,188.6133	$1,188.61	$1,188.60	$1,188.70