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	$166.92	10.522%	$184.4833	$184.48	$184.50	$184.50
Purchase #2	$32.89	4.171%	$34.2618	$34.26	$34.25	$34.30
Purchase #3	$127.89	12.515%	$143.8954	$143.90	$143.90	$143.90
Purchase #4	$198.62	6.531%	$211.5919	$211.59	$211.60	$211.60
Purchase #5	$196.72	11.779%	$219.8916	$219.89	$219.90	$219.90
Purchase #6	$55.55	13.634%	$63.1237	$63.12	$63.10	$63.10
Purchase #7	$42.55	10.383%	$46.968	$46.97	$46.95	$47.00
7 purchase totals =	$821.14		$904.2157	$904.21	$904.20	$904.30