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	$164.67	7.341%	$176.7584	$176.76	$176.75	$176.80
Purchase #2	$120.98	8.400%	$131.1423	$131.14	$131.15	$131.10
Purchase #3	$8.97	6.363%	$9.5408	$9.54	$9.55	$9.50
Purchase #4	$40.66	4.792%	$42.6084	$42.61	$42.60	$42.60
Purchase #5	$241.47	6.124%	$256.2576	$256.26	$256.25	$256.30
Purchase #6	$145.50	11.833%	$162.717	$162.72	$162.70	$162.70
Purchase #7	$78.75	12.179%	$88.341	$88.34	$88.35	$88.30
7 purchase totals =	$801.00		$867.3655	$867.37	$867.35	$867.30