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	$118.40	11.362%	$131.8526	$131.85	$131.85	$131.90
Purchase #2	$233.70	8.209%	$252.8844	$252.88	$252.90	$252.90
Purchase #3	$40.83	4.487%	$42.662	$42.66	$42.65	$42.70
Purchase #4	$49.41	10.225%	$54.4622	$54.46	$54.45	$54.50
Purchase #5	$66.62	3.347%	$68.8498	$68.85	$68.85	$68.80
Purchase #6	$86.74	4.790%	$90.8948	$90.89	$90.90	$90.90
Purchase #7	$52.84	10.806%	$58.5499	$58.55	$58.55	$58.50
7 purchase totals =	$648.54		$700.1557	$700.14	$700.15	$700.20