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	$10.78	5.236%	$11.3444	$11.34	$11.35	$11.30
Purchase #2	$85.39	11.190%	$94.9451	$94.95	$94.95	$94.90
Purchase #3	$226.41	3.276%	$233.8272	$233.83	$233.85	$233.80
Purchase #4	$172.76	7.807%	$186.2474	$186.25	$186.25	$186.20
Purchase #5	$196.59	10.568%	$217.3656	$217.37	$217.35	$217.40
Purchase #6	$145.37	4.400%	$151.7663	$151.77	$151.75	$151.80
Purchase #7	$140.52	3.292%	$145.1459	$145.15	$145.15	$145.10
7 purchase totals =	$977.82		$1,040.6419	$1,040.66	$1,040.65	$1,040.50