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	$38.59	11.205%	$42.914	$42.91	$42.90	$42.90
Purchase #2	$216.37	4.268%	$225.6047	$225.60	$225.60	$225.60
Purchase #3	$197.87	9.420%	$216.5094	$216.51	$216.50	$216.50
Purchase #4	$9.61	5.241%	$10.1137	$10.11	$10.10	$10.10
Purchase #5	$102.27	4.515%	$106.8875	$106.89	$106.90	$106.90
Purchase #6	$142.98	13.401%	$162.1407	$162.14	$162.15	$162.10
Purchase #7	$231.76	4.579%	$242.3723	$242.37	$242.35	$242.40
7 purchase totals =	$939.45		$1,006.5423	$1,006.53	$1,006.50	$1,006.50