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	$223.28	5.327%	$235.1741	$235.17	$235.15	$235.20
Purchase #2	$92.59	12.621%	$104.2758	$104.28	$104.30	$104.30
Purchase #3	$150.32	12.327%	$168.8499	$168.85	$168.85	$168.80
Purchase #4	$178.59	13.296%	$202.3353	$202.34	$202.35	$202.30
Purchase #5	$42.71	13.819%	$48.6121	$48.61	$48.60	$48.60
Purchase #6	$101.49	3.618%	$105.1619	$105.16	$105.15	$105.20
Purchase #7	$226.31	5.638%	$239.0694	$239.07	$239.05	$239.10
7 purchase totals =	$1,015.29		$1,103.4785	$1,103.48	$1,103.45	$1,103.50