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	$115.63	12.654%	$130.2618	$130.26	$130.25	$130.30
Purchase #2	$239.88	6.819%	$256.2374	$256.24	$256.25	$256.20
Purchase #3	$60.60	12.254%	$68.0259	$68.03	$68.05	$68.00
Purchase #4	$58.57	13.460%	$66.4535	$66.45	$66.45	$66.50
Purchase #5	$139.82	3.372%	$144.5347	$144.53	$144.55	$144.50
Purchase #6	$142.47	4.531%	$148.9253	$148.93	$148.95	$148.90
Purchase #7	$221.98	11.504%	$247.5166	$247.52	$247.50	$247.50
7 purchase totals =	$978.95		$1,061.9552	$1,061.96	$1,062.00	$1,061.90