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	$192.53	12.146%	$215.9147	$215.91	$215.90	$215.90
Purchase #2	$211.83	10.138%	$233.3053	$233.31	$233.30	$233.30
Purchase #3	$24.88	3.147%	$25.663	$25.66	$25.65	$25.70
Purchase #4	$176.32	11.667%	$196.8913	$196.89	$196.90	$196.90
Purchase #5	$242.88	9.832%	$266.76	$266.76	$266.75	$266.80
Purchase #6	$228.59	11.182%	$254.1509	$254.15	$254.15	$254.20
Purchase #7	$174.87	12.578%	$196.8651	$196.87	$196.85	$196.90
7 purchase totals =	$1,251.90		$1,389.5503	$1,389.55	$1,389.50	$1,389.70