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	$136.80	7.238%	$146.7016	$146.70	$146.70	$146.70
Purchase #2	$118.47	7.230%	$127.0354	$127.04	$127.05	$127.00
Purchase #3	$224.41	4.761%	$235.0942	$235.09	$235.10	$235.10
Purchase #4	$195.57	7.870%	$210.9614	$210.96	$210.95	$211.00
Purchase #5	$115.87	9.631%	$127.0294	$127.03	$127.05	$127.00
Purchase #6	$139.57	3.128%	$143.9357	$143.94	$143.95	$143.90
Purchase #7	$50.84	4.643%	$53.2005	$53.20	$53.20	$53.20
7 purchase totals =	$981.53		$1,043.9582	$1,043.96	$1,044.00	$1,043.90