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	$145.81	3.129%	$150.3724	$150.37	$150.35	$150.40
Purchase #2	$89.64	8.128%	$96.9259	$96.93	$96.95	$96.90
Purchase #3	$143.54	10.318%	$158.3505	$158.35	$158.35	$158.40
Purchase #4	$124.51	6.374%	$132.4463	$132.45	$132.45	$132.40
Purchase #5	$84.43	7.552%	$90.8062	$90.81	$90.80	$90.80
Purchase #6	$187.31	5.774%	$198.1253	$198.13	$198.15	$198.10
Purchase #7	$95.35	6.400%	$101.4524	$101.45	$101.45	$101.50
7 purchase totals =	$870.59		$928.4790	$928.49	$928.50	$928.50