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	$83.47	4.478%	$87.2078	$87.21	$87.20	$87.20
Purchase #2	$196.32	4.680%	$205.5078	$205.51	$205.50	$205.50
Purchase #3	$142.93	5.552%	$150.8655	$150.87	$150.85	$150.90
Purchase #4	$158.79	6.335%	$168.8493	$168.85	$168.85	$168.80
Purchase #5	$222.85	9.516%	$244.0564	$244.06	$244.05	$244.10
Purchase #6	$9.50	7.849%	$10.2457	$10.25	$10.25	$10.20
Purchase #7	$176.90	9.545%	$193.7851	$193.79	$193.80	$193.80
7 purchase totals =	$990.76		$1,060.5176	$1,060.54	$1,060.50	$1,060.50