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	$187.57	12.732%	$211.4514	$211.45	$211.45	$211.50
Purchase #2	$77.96	12.610%	$87.7908	$87.79	$87.80	$87.80
Purchase #3	$16.26	13.546%	$18.4626	$18.46	$18.45	$18.50
Purchase #4	$148.56	3.436%	$153.6645	$153.66	$153.65	$153.70
Purchase #5	$196.53	6.110%	$208.538	$208.54	$208.55	$208.50
Purchase #6	$101.32	10.307%	$111.7631	$111.76	$111.75	$111.80
Purchase #7	$192.78	9.160%	$210.4386	$210.44	$210.45	$210.40
7 purchase totals =	$920.98		$1,002.1090	$1,002.10	$1,002.10	$1,002.20