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	$102.46	9.191%	$111.8771	$111.88	$111.90	$111.90
Purchase #2	$148.81	7.293%	$159.6627	$159.66	$159.65	$159.70
Purchase #3	$171.41	6.626%	$182.7676	$182.77	$182.75	$182.80
Purchase #4	$141.87	3.683%	$147.0951	$147.10	$147.10	$147.10
Purchase #5	$111.58	9.735%	$122.4423	$122.44	$122.45	$122.40
Purchase #6	$237.42	9.682%	$260.407	$260.41	$260.40	$260.40
Purchase #7	$92.46	8.311%	$100.1444	$100.14	$100.15	$100.10
7 purchase totals =	$1,006.01		$1,084.3962	$1,084.40	$1,084.40	$1,084.40