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	$172.38	10.741%	$190.8953	$190.90	$190.90	$190.90
Purchase #2	$74.89	4.521%	$78.2758	$78.28	$78.30	$78.30
Purchase #3	$245.47	11.652%	$274.0722	$274.07	$274.05	$274.10
Purchase #4	$238.37	13.855%	$271.3962	$271.40	$271.40	$271.40
Purchase #5	$80.65	7.787%	$86.9302	$86.93	$86.95	$86.90
Purchase #6	$46.89	5.164%	$49.3114	$49.31	$49.30	$49.30
Purchase #7	$151.58	10.861%	$168.0431	$168.04	$168.05	$168.00
7 purchase totals =	$1,010.23		$1,118.9242	$1,118.93	$1,118.95	$1,118.90