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	$232.94	12.610%	$262.3137	$262.31	$262.30	$262.30
Purchase #2	$16.41	13.651%	$18.6501	$18.65	$18.65	$18.70
Purchase #3	$244.75	5.646%	$258.5686	$258.57	$258.55	$258.60
Purchase #4	$37.60	12.804%	$42.4143	$42.41	$42.40	$42.40
Purchase #5	$85.55	11.653%	$95.5191	$95.52	$95.50	$95.50
Purchase #6	$90.55	13.193%	$102.4963	$102.50	$102.50	$102.50
Purchase #7	$165.62	9.152%	$180.7775	$180.78	$180.80	$180.80
7 purchase totals =	$873.42		$960.7396	$960.74	$960.70	$960.80