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	$55.31	7.189%	$59.2862	$59.29	$59.30	$59.30
Purchase #2	$71.58	8.770%	$77.8576	$77.86	$77.85	$77.90
Purchase #3	$200.42	3.299%	$207.0319	$207.03	$207.05	$207.00
Purchase #4	$78.74	12.495%	$88.5786	$88.58	$88.60	$88.60
Purchase #5	$78.82	4.207%	$82.136	$82.14	$82.15	$82.10
Purchase #6	$103.73	7.756%	$111.7753	$111.78	$111.80	$111.80
Purchase #7	$178.54	10.668%	$197.5866	$197.59	$197.60	$197.60
7 purchase totals =	$767.14		$824.2522	$824.27	$824.35	$824.30