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	$216.57	12.732%	$244.1437	$244.14	$244.15	$244.10
Purchase #2	$78.47	13.577%	$89.1239	$89.12	$89.10	$89.10
Purchase #3	$33.35	3.863%	$34.6383	$34.64	$34.65	$34.60
Purchase #4	$151.39	4.655%	$158.4372	$158.44	$158.45	$158.40
Purchase #5	$204.50	3.238%	$211.1217	$211.12	$211.10	$211.10
Purchase #6	$166.99	10.119%	$183.8877	$183.89	$183.90	$183.90
Purchase #7	$33.65	10.350%	$37.1328	$37.13	$37.15	$37.10
7 purchase totals =	$884.92		$958.4853	$958.48	$958.50	$958.30