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	$192.77	12.522%	$216.9087	$216.91	$216.90	$216.90
Purchase #2	$72.77	11.389%	$81.0578	$81.06	$81.05	$81.10
Purchase #3	$141.51	6.244%	$150.3459	$150.35	$150.35	$150.30
Purchase #4	$70.66	11.623%	$78.8728	$78.87	$78.85	$78.90
Purchase #5	$95.34	6.413%	$101.4542	$101.45	$101.45	$101.50
Purchase #6	$53.89	12.775%	$60.7744	$60.77	$60.75	$60.80
Purchase #7	$158.95	8.232%	$172.0348	$172.03	$172.05	$172.00
7 purchase totals =	$785.89		$861.4486	$861.44	$861.40	$861.50