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	$219.32	3.627%	$227.2747	$227.27	$227.25	$227.30
Purchase #2	$157.97	9.428%	$172.8634	$172.86	$172.85	$172.90
Purchase #3	$80.44	12.136%	$90.2022	$90.20	$90.20	$90.20
Purchase #4	$180.81	13.390%	$205.0205	$205.02	$205.00	$205.00
Purchase #5	$130.82	10.135%	$144.0786	$144.08	$144.10	$144.10
Purchase #6	$227.74	5.788%	$240.9216	$240.92	$240.90	$240.90
Purchase #7	$225.95	3.776%	$234.4819	$234.48	$234.50	$234.50
7 purchase totals =	$1,223.05		$1,314.8429	$1,314.83	$1,314.80	$1,314.90