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	$94.42	11.476%	$105.2556	$105.26	$105.25	$105.30
Purchase #2	$238.88	8.622%	$259.4762	$259.48	$259.50	$259.50
Purchase #3	$88.94	7.799%	$95.8764	$95.88	$95.90	$95.90
Purchase #4	$74.46	8.528%	$80.8099	$80.81	$80.80	$80.80
Purchase #5	$173.55	3.146%	$179.0099	$179.01	$179.00	$179.00
Purchase #6	$111.54	12.850%	$125.8729	$125.87	$125.85	$125.90
Purchase #7	$248.75	3.166%	$256.6254	$256.63	$256.65	$256.60
7 purchase totals =	$1,030.54		$1,102.9263	$1,102.94	$1,102.95	$1,103.00