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	$23.61	8.534%	$25.6249	$25.62	$25.60	$25.60
Purchase #2	$138.70	8.563%	$150.5769	$150.58	$150.60	$150.60
Purchase #3	$163.35	13.734%	$185.7845	$185.78	$185.80	$185.80
Purchase #4	$244.98	12.272%	$275.0439	$275.04	$275.05	$275.00
Purchase #5	$131.61	11.647%	$146.9386	$146.94	$146.95	$146.90
Purchase #6	$190.29	4.648%	$199.1347	$199.13	$199.15	$199.10
Purchase #7	$109.90	12.607%	$123.7551	$123.76	$123.75	$123.80
7 purchase totals =	$1,002.44		$1,106.8586	$1,106.85	$1,106.90	$1,106.80