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	$246.76	3.840%	$256.2356	$256.24	$256.25	$256.20
Purchase #2	$179.83	11.117%	$199.8217	$199.82	$199.80	$199.80
Purchase #3	$72.35	3.389%	$74.8019	$74.80	$74.80	$74.80
Purchase #4	$126.56	4.811%	$132.6488	$132.65	$132.65	$132.60
Purchase #5	$28.90	8.705%	$31.4157	$31.42	$31.40	$31.40
Purchase #6	$198.47	12.117%	$222.5186	$222.52	$222.50	$222.50
Purchase #7	$229.34	3.733%	$237.9013	$237.90	$237.90	$237.90
7 purchase totals =	$1,082.21		$1,155.3436	$1,155.35	$1,155.30	$1,155.20