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	$101.95	3.624%	$105.6447	$105.64	$105.65	$105.60
Purchase #2	$238.58	7.255%	$255.889	$255.89	$255.90	$255.90
Purchase #3	$217.59	5.528%	$229.6184	$229.62	$229.60	$229.60
Purchase #4	$163.86	3.202%	$169.1068	$169.11	$169.10	$169.10
Purchase #5	$95.86	12.472%	$107.8157	$107.82	$107.80	$107.80
Purchase #6	$100.31	5.572%	$105.8993	$105.90	$105.90	$105.90
Purchase #7	$223.63	9.607%	$245.1141	$245.11	$245.10	$245.10
7 purchase totals =	$1,141.78		$1,219.0880	$1,219.09	$1,219.05	$1,219.00