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	$177.38	12.405%	$199.384	$199.38	$199.40	$199.40
Purchase #2	$210.66	13.738%	$239.6005	$239.60	$239.60	$239.60
Purchase #3	$86.72	4.179%	$90.344	$90.34	$90.35	$90.30
Purchase #4	$102.87	4.180%	$107.17	$107.17	$107.15	$107.20
Purchase #5	$186.70	10.217%	$205.7751	$205.78	$205.80	$205.80
Purchase #6	$7.85	3.650%	$8.1365	$8.14	$8.15	$8.10
Purchase #7	$186.86	12.868%	$210.9051	$210.91	$210.90	$210.90
7 purchase totals =	$959.04		$1,061.3152	$1,061.32	$1,061.35	$1,061.30