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	$40.54	4.495%	$42.3623	$42.36	$42.35	$42.40
Purchase #2	$32.90	13.224%	$37.2507	$37.25	$37.25	$37.30
Purchase #3	$67.63	5.405%	$71.2854	$71.29	$71.30	$71.30
Purchase #4	$98.70	10.630%	$109.1918	$109.19	$109.20	$109.20
Purchase #5	$163.95	13.614%	$186.2702	$186.27	$186.25	$186.30
Purchase #6	$129.65	11.572%	$144.6531	$144.65	$144.65	$144.70
Purchase #7	$31.28	10.305%	$34.5034	$34.50	$34.50	$34.50
7 purchase totals =	$564.65		$625.5169	$625.51	$625.50	$625.70