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	$195.28	10.384%	$215.5579	$215.56	$215.55	$215.60
Purchase #2	$96.54	11.392%	$107.5378	$107.54	$107.55	$107.50
Purchase #3	$85.92	4.827%	$90.0674	$90.07	$90.05	$90.10
Purchase #4	$59.52	12.213%	$66.7892	$66.79	$66.80	$66.80
Purchase #5	$150.89	13.310%	$170.9735	$170.97	$170.95	$171.00
Purchase #6	$139.36	13.268%	$157.8503	$157.85	$157.85	$157.90
Purchase #7	$67.35	7.448%	$72.3662	$72.37	$72.35	$72.40
7 purchase totals =	$794.86		$881.1423	$881.15	$881.10	$881.30