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	$138.35	9.353%	$151.2899	$151.29	$151.30	$151.30
Purchase #2	$130.29	12.616%	$146.7274	$146.73	$146.75	$146.70
Purchase #3	$239.44	5.477%	$252.5541	$252.55	$252.55	$252.60
Purchase #4	$174.96	10.185%	$192.7797	$192.78	$192.80	$192.80
Purchase #5	$105.41	7.667%	$113.4918	$113.49	$113.50	$113.50
Purchase #6	$71.54	10.199%	$78.8364	$78.84	$78.85	$78.80
Purchase #7	$163.55	7.368%	$175.6004	$175.60	$175.60	$175.60
7 purchase totals =	$1,023.54		$1,111.2797	$1,111.28	$1,111.35	$1,111.30