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	$192.79	8.345%	$208.8783	$208.88	$208.90	$208.90
Purchase #2	$42.92	5.146%	$45.1287	$45.13	$45.15	$45.10
Purchase #3	$88.77	5.446%	$93.6044	$93.60	$93.60	$93.60
Purchase #4	$80.68	10.658%	$89.2789	$89.28	$89.30	$89.30
Purchase #5	$118.97	13.168%	$134.636	$134.64	$134.65	$134.60
Purchase #6	$16.74	3.429%	$17.314	$17.31	$17.30	$17.30
Purchase #7	$69.76	5.111%	$73.3254	$73.33	$73.35	$73.30
7 purchase totals =	$610.63		$662.1657	$662.17	$662.25	$662.10