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	$72.69	7.640%	$78.2435	$78.24	$78.25	$78.20
Purchase #2	$93.94	7.419%	$100.9094	$100.91	$100.90	$100.90
Purchase #3	$38.71	13.659%	$43.9974	$44.00	$44.00	$44.00
Purchase #4	$77.78	6.707%	$82.9967	$83.00	$83.00	$83.00
Purchase #5	$212.32	7.854%	$228.9956	$229.00	$229.00	$229.00
Purchase #6	$205.31	12.829%	$231.6492	$231.65	$231.65	$231.60
Purchase #7	$118.80	11.595%	$132.5749	$132.57	$132.55	$132.60
7 purchase totals =	$819.55		$899.3667	$899.37	$899.35	$899.30