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	$232.66	9.147%	$253.9414	$253.94	$253.95	$253.90
Purchase #2	$184.97	7.328%	$198.5246	$198.52	$198.50	$198.50
Purchase #3	$81.42	10.873%	$90.2728	$90.27	$90.25	$90.30
Purchase #4	$246.69	8.874%	$268.5813	$268.58	$268.60	$268.60
Purchase #5	$36.95	10.808%	$40.9436	$40.94	$40.95	$40.90
Purchase #6	$245.72	13.705%	$279.3959	$279.40	$279.40	$279.40
Purchase #7	$222.89	12.102%	$249.8641	$249.86	$249.85	$249.90
7 purchase totals =	$1,251.30		$1,381.5237	$1,381.51	$1,381.50	$1,381.50