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	$144.59	6.766%	$154.373	$154.37	$154.35	$154.40
Purchase #2	$93.54	6.452%	$99.5752	$99.58	$99.60	$99.60
Purchase #3	$91.95	3.657%	$95.3126	$95.31	$95.30	$95.30
Purchase #4	$99.60	12.545%	$112.0948	$112.09	$112.10	$112.10
Purchase #5	$133.60	5.521%	$140.9761	$140.98	$141.00	$141.00
Purchase #6	$65.56	6.172%	$69.6064	$69.61	$69.60	$69.60
Purchase #7	$136.78	5.526%	$144.3385	$144.34	$144.35	$144.30
7 purchase totals =	$765.62		$816.2766	$816.28	$816.30	$816.30