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	$197.56	9.592%	$216.51	$216.51	$216.50	$216.50
Purchase #2	$93.52	6.431%	$99.5343	$99.53	$99.55	$99.50
Purchase #3	$196.54	7.597%	$211.4711	$211.47	$211.45	$211.50
Purchase #4	$55.85	13.753%	$63.5311	$63.53	$63.55	$63.50
Purchase #5	$13.93	11.340%	$15.5097	$15.51	$15.50	$15.50
Purchase #6	$217.53	9.494%	$238.1823	$238.18	$238.20	$238.20
Purchase #7	$157.35	10.398%	$173.7113	$173.71	$173.70	$173.70
7 purchase totals =	$932.28		$1,018.4498	$1,018.44	$1,018.45	$1,018.40