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	$205.52	5.856%	$217.5553	$217.56	$217.55	$217.60
Purchase #2	$77.41	6.124%	$82.1506	$82.15	$82.15	$82.20
Purchase #3	$142.83	6.361%	$151.9154	$151.92	$151.90	$151.90
Purchase #4	$88.33	11.579%	$98.5577	$98.56	$98.55	$98.60
Purchase #5	$53.60	10.513%	$59.235	$59.24	$59.25	$59.20
Purchase #6	$136.96	8.154%	$148.1277	$148.13	$148.15	$148.10
Purchase #7	$20.64	4.193%	$21.5054	$21.51	$21.50	$21.50
7 purchase totals =	$725.29		$779.0471	$779.07	$779.05	$779.10