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	$54.78	8.271%	$59.3109	$59.31	$59.30	$59.30
Purchase #2	$19.43	5.758%	$20.5488	$20.55	$20.55	$20.50
Purchase #3	$45.99	5.306%	$48.4302	$48.43	$48.45	$48.40
Purchase #4	$112.64	11.162%	$125.2129	$125.21	$125.20	$125.20
Purchase #5	$96.98	4.287%	$101.1375	$101.14	$101.15	$101.10
Purchase #6	$219.97	9.844%	$241.6238	$241.62	$241.60	$241.60
Purchase #7	$35.61	4.684%	$37.278	$37.28	$37.30	$37.30
7 purchase totals =	$585.40		$633.5421	$633.54	$633.55	$633.40