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	$182.35	5.647%	$192.6473	$192.65	$192.65	$192.60
Purchase #2	$164.89	9.679%	$180.8497	$180.85	$180.85	$180.80
Purchase #3	$249.85	11.731%	$279.1599	$279.16	$279.15	$279.20
Purchase #4	$189.73	9.293%	$207.3616	$207.36	$207.35	$207.40
Purchase #5	$30.33	5.164%	$31.8962	$31.90	$31.90	$31.90
Purchase #6	$52.59	5.358%	$55.4078	$55.41	$55.40	$55.40
Purchase #7	$14.60	5.849%	$15.454	$15.45	$15.45	$15.50
7 purchase totals =	$884.34		$962.7765	$962.78	$962.75	$962.80