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	$70.60	3.159%	$72.8303	$72.83	$72.85	$72.80
Purchase #2	$206.80	3.449%	$213.9325	$213.93	$213.95	$213.90
Purchase #3	$19.59	7.427%	$21.0449	$21.04	$21.05	$21.00
Purchase #4	$176.45	11.839%	$197.3399	$197.34	$197.35	$197.30
Purchase #5	$206.96	8.123%	$223.7714	$223.77	$223.75	$223.80
Purchase #6	$180.91	6.406%	$192.4991	$192.50	$192.50	$192.50
Purchase #7	$75.57	6.707%	$80.6385	$80.64	$80.65	$80.60
7 purchase totals =	$936.88		$1,002.0566	$1,002.05	$1,002.10	$1,001.90