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	$234.38	12.244%	$263.0775	$263.08	$263.10	$263.10
Purchase #2	$166.31	7.240%	$178.3508	$178.35	$178.35	$178.40
Purchase #3	$82.49	7.758%	$88.8896	$88.89	$88.90	$88.90
Purchase #4	$197.94	11.713%	$221.1247	$221.12	$221.10	$221.10
Purchase #5	$104.85	9.236%	$114.5339	$114.53	$114.55	$114.50
Purchase #6	$82.74	3.797%	$85.8816	$85.88	$85.90	$85.90
Purchase #7	$52.82	3.490%	$54.6634	$54.66	$54.65	$54.70
7 purchase totals =	$921.53		$1,006.5215	$1,006.51	$1,006.55	$1,006.60