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	$114.95	6.419%	$122.3286	$122.33	$122.35	$122.30
Purchase #2	$84.82	6.713%	$90.514	$90.51	$90.50	$90.50
Purchase #3	$87.30	13.710%	$99.2688	$99.27	$99.25	$99.30
Purchase #4	$34.72	7.776%	$37.4198	$37.42	$37.40	$37.40
Purchase #5	$123.42	4.332%	$128.7666	$128.77	$128.75	$128.80
Purchase #6	$215.56	7.554%	$231.8434	$231.84	$231.85	$231.80
Purchase #7	$224.71	4.420%	$234.6422	$234.64	$234.65	$234.60
7 purchase totals =	$885.48		$944.7834	$944.78	$944.75	$944.70