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	$35.62	3.339%	$36.8094	$36.81	$36.80	$36.80
Purchase #2	$89.93	9.189%	$98.1937	$98.19	$98.20	$98.20
Purchase #3	$23.85	11.209%	$26.5233	$26.52	$26.50	$26.50
Purchase #4	$63.54	12.164%	$71.269	$71.27	$71.25	$71.30
Purchase #5	$77.56	6.187%	$82.3586	$82.36	$82.35	$82.40
Purchase #6	$33.81	11.212%	$37.6008	$37.60	$37.60	$37.60
Purchase #7	$162.96	6.232%	$173.1157	$173.12	$173.10	$173.10
7 purchase totals =	$487.27		$525.8705	$525.87	$525.80	$525.90