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	$112.65	3.702%	$116.8203	$116.82	$116.80	$116.80
Purchase #2	$216.28	7.809%	$233.1693	$233.17	$233.15	$233.20
Purchase #3	$99.59	6.524%	$106.0873	$106.09	$106.10	$106.10
Purchase #4	$38.82	5.494%	$40.9528	$40.95	$40.95	$41.00
Purchase #5	$38.86	4.134%	$40.4665	$40.47	$40.45	$40.50
Purchase #6	$173.36	8.627%	$188.3158	$188.32	$188.30	$188.30
Purchase #7	$131.45	4.180%	$136.9446	$136.94	$136.95	$136.90
7 purchase totals =	$811.01		$862.7566	$862.76	$862.70	$862.80