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	$98.31	13.377%	$111.4609	$111.46	$111.45	$111.50
Purchase #2	$74.89	12.596%	$84.3231	$84.32	$84.30	$84.30
Purchase #3	$126.83	13.130%	$143.4828	$143.48	$143.50	$143.50
Purchase #4	$232.85	5.705%	$246.1341	$246.13	$246.15	$246.10
Purchase #5	$66.33	5.241%	$69.8064	$69.81	$69.80	$69.80
Purchase #6	$29.93	7.420%	$32.1508	$32.15	$32.15	$32.20
Purchase #7	$43.96	12.735%	$49.5583	$49.56	$49.55	$49.60
7 purchase totals =	$673.10		$736.9164	$736.91	$736.90	$737.00