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	$213.50	11.168%	$237.3437	$237.34	$237.35	$237.30
Purchase #2	$235.95	8.235%	$255.3805	$255.38	$255.40	$255.40
Purchase #3	$227.44	6.231%	$241.6118	$241.61	$241.60	$241.60
Purchase #4	$136.57	8.294%	$147.8971	$147.90	$147.90	$147.90
Purchase #5	$80.39	11.205%	$89.3977	$89.40	$89.40	$89.40
Purchase #6	$83.91	9.363%	$91.7665	$91.77	$91.75	$91.80
Purchase #7	$21.98	6.253%	$23.3544	$23.35	$23.35	$23.40
7 purchase totals =	$999.74		$1,086.7517	$1,086.75	$1,086.75	$1,086.80