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	$92.35	13.225%	$104.5633	$104.56	$104.55	$104.60
Purchase #2	$209.87	4.119%	$218.5145	$218.51	$218.50	$218.50
Purchase #3	$155.53	13.472%	$176.483	$176.48	$176.50	$176.50
Purchase #4	$143.26	5.470%	$151.0963	$151.10	$151.10	$151.10
Purchase #5	$170.39	11.336%	$189.7054	$189.71	$189.70	$189.70
Purchase #6	$45.42	6.382%	$48.3187	$48.32	$48.30	$48.30
Purchase #7	$80.66	7.225%	$86.4877	$86.49	$86.50	$86.50
7 purchase totals =	$897.48		$975.1689	$975.17	$975.15	$975.20