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	$156.81	9.375%	$171.5109	$171.51	$171.50	$171.50
Purchase #2	$135.36	13.298%	$153.3602	$153.36	$153.35	$153.40
Purchase #3	$10.31	12.143%	$11.5619	$11.56	$11.55	$11.60
Purchase #4	$54.66	3.507%	$56.5769	$56.58	$56.60	$56.60
Purchase #5	$58.25	8.419%	$63.1541	$63.15	$63.15	$63.20
Purchase #6	$56.76	5.437%	$59.846	$59.85	$59.85	$59.80
Purchase #7	$44.45	3.803%	$46.1404	$46.14	$46.15	$46.10
7 purchase totals =	$516.60		$562.1504	$562.15	$562.15	$562.20