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	$153.95	8.620%	$167.2205	$167.22	$167.20	$167.20
Purchase #2	$99.47	12.516%	$111.9197	$111.92	$111.90	$111.90
Purchase #3	$92.56	8.565%	$100.4878	$100.49	$100.50	$100.50
Purchase #4	$238.48	10.192%	$262.7859	$262.79	$262.80	$262.80
Purchase #5	$135.56	5.318%	$142.7691	$142.77	$142.75	$142.80
Purchase #6	$51.94	10.742%	$57.5194	$57.52	$57.50	$57.50
Purchase #7	$132.87	10.701%	$147.0884	$147.09	$147.10	$147.10
7 purchase totals =	$904.83		$989.7908	$989.80	$989.75	$989.80