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	$111.82	13.509%	$126.9258	$126.93	$126.95	$126.90
Purchase #2	$133.35	5.213%	$140.3015	$140.30	$140.30	$140.30
Purchase #3	$196.50	7.658%	$211.548	$211.55	$211.55	$211.50
Purchase #4	$118.97	6.768%	$127.0219	$127.02	$127.00	$127.00
Purchase #5	$49.90	8.857%	$54.3196	$54.32	$54.30	$54.30
Purchase #6	$68.65	5.351%	$72.3235	$72.32	$72.30	$72.30
Purchase #7	$196.67	10.105%	$216.5435	$216.54	$216.55	$216.50
7 purchase totals =	$875.86		$948.9838	$948.98	$948.95	$948.80