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	$93.95	11.527%	$104.7796	$104.78	$104.80	$104.80
Purchase #2	$58.29	4.362%	$60.8326	$60.83	$60.85	$60.80
Purchase #3	$244.30	10.340%	$269.5606	$269.56	$269.55	$269.60
Purchase #4	$40.50	7.673%	$43.6076	$43.61	$43.60	$43.60
Purchase #5	$231.94	7.137%	$248.4936	$248.49	$248.50	$248.50
Purchase #6	$230.55	10.362%	$254.4396	$254.44	$254.45	$254.40
Purchase #7	$123.31	10.412%	$136.149	$136.15	$136.15	$136.10
7 purchase totals =	$1,022.84		$1,117.8626	$1,117.86	$1,117.90	$1,117.80