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	$19.72	10.800%	$21.8498	$21.85	$21.85	$21.80
Purchase #2	$222.70	12.136%	$249.7269	$249.73	$249.75	$249.70
Purchase #3	$234.58	4.627%	$245.434	$245.43	$245.45	$245.40
Purchase #4	$105.64	3.380%	$109.2106	$109.21	$109.20	$109.20
Purchase #5	$186.39	12.808%	$210.2628	$210.26	$210.25	$210.30
Purchase #6	$78.36	3.797%	$81.3353	$81.34	$81.35	$81.30
Purchase #7	$123.42	3.613%	$127.8792	$127.88	$127.90	$127.90
7 purchase totals =	$970.81		$1,045.6986	$1,045.70	$1,045.75	$1,045.60