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	$156.89	12.163%	$175.9725	$175.97	$175.95	$176.00
Purchase #2	$163.75	9.860%	$179.8958	$179.90	$179.90	$179.90
Purchase #3	$203.67	7.577%	$219.1021	$219.10	$219.10	$219.10
Purchase #4	$56.91	4.366%	$59.3947	$59.39	$59.40	$59.40
Purchase #5	$81.64	4.490%	$85.3056	$85.31	$85.30	$85.30
Purchase #6	$197.51	5.720%	$208.8076	$208.81	$208.80	$208.80
Purchase #7	$207.82	6.546%	$221.4239	$221.42	$221.40	$221.40
7 purchase totals =	$1,068.19		$1,149.9022	$1,149.90	$1,149.85	$1,149.90