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	$239.73	5.300%	$252.4357	$252.44	$252.45	$252.40
Purchase #2	$39.51	7.786%	$42.5862	$42.59	$42.60	$42.60
Purchase #3	$167.48	5.413%	$176.5457	$176.55	$176.55	$176.50
Purchase #4	$194.83	4.103%	$202.8239	$202.82	$202.80	$202.80
Purchase #5	$250.47	13.741%	$284.8871	$284.89	$284.90	$284.90
Purchase #6	$50.77	13.414%	$57.5803	$57.58	$57.60	$57.60
Purchase #7	$212.66	4.653%	$222.5551	$222.56	$222.55	$222.60
7 purchase totals =	$1,155.45		$1,239.4140	$1,239.43	$1,239.45	$1,239.40