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	$8.96	11.749%	$10.0127	$10.01	$10.00	$10.00
Purchase #2	$204.34	3.133%	$210.742	$210.74	$210.75	$210.70
Purchase #3	$115.94	8.618%	$125.9317	$125.93	$125.95	$125.90
Purchase #4	$235.34	8.518%	$255.3863	$255.39	$255.40	$255.40
Purchase #5	$186.31	5.238%	$196.0689	$196.07	$196.05	$196.10
Purchase #6	$178.73	3.599%	$185.1625	$185.16	$185.15	$185.20
Purchase #7	$127.83	11.821%	$142.9408	$142.94	$142.95	$142.90
7 purchase totals =	$1,057.45		$1,126.2449	$1,126.24	$1,126.25	$1,126.20