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	$35.69	5.333%	$37.5933	$37.59	$37.60	$37.60
Purchase #2	$157.96	4.139%	$164.498	$164.50	$164.50	$164.50
Purchase #3	$244.91	10.727%	$271.1815	$271.18	$271.20	$271.20
Purchase #4	$59.72	6.713%	$63.729	$63.73	$63.75	$63.70
Purchase #5	$234.77	9.389%	$256.8126	$256.81	$256.80	$256.80
Purchase #6	$189.37	10.606%	$209.4546	$209.45	$209.45	$209.50
Purchase #7	$30.30	6.203%	$32.1795	$32.18	$32.20	$32.20
7 purchase totals =	$952.72		$1,035.4485	$1,035.44	$1,035.50	$1,035.50