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	$193.38	8.843%	$210.4806	$210.48	$210.50	$210.50
Purchase #2	$173.41	3.729%	$179.8765	$179.88	$179.90	$179.90
Purchase #3	$9.72	4.297%	$10.1377	$10.14	$10.15	$10.10
Purchase #4	$188.58	4.191%	$196.4834	$196.48	$196.50	$196.50
Purchase #5	$27.75	3.348%	$28.6791	$28.68	$28.70	$28.70
Purchase #6	$157.48	4.510%	$164.5823	$164.58	$164.60	$164.60
Purchase #7	$210.83	9.688%	$231.2552	$231.26	$231.25	$231.30
7 purchase totals =	$961.15		$1,021.4948	$1,021.50	$1,021.60	$1,021.60