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	$198.27	12.226%	$222.5105	$222.51	$222.50	$222.50
Purchase #2	$95.83	8.319%	$103.8021	$103.80	$103.80	$103.80
Purchase #3	$115.76	10.312%	$127.6972	$127.70	$127.70	$127.70
Purchase #4	$129.33	13.548%	$146.8516	$146.85	$146.85	$146.90
Purchase #5	$97.49	5.625%	$102.9738	$102.97	$102.95	$103.00
Purchase #6	$147.98	11.152%	$164.4827	$164.48	$164.50	$164.50
Purchase #7	$210.94	7.369%	$226.4842	$226.48	$226.50	$226.50
7 purchase totals =	$995.60		$1,094.8021	$1,094.79	$1,094.80	$1,094.90