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	$98.47	13.324%	$111.5901	$111.59	$111.60	$111.60
Purchase #2	$247.83	5.384%	$261.1732	$261.17	$261.15	$261.20
Purchase #3	$222.44	5.134%	$233.8601	$233.86	$233.85	$233.90
Purchase #4	$59.83	3.720%	$62.0557	$62.06	$62.05	$62.10
Purchase #5	$190.51	3.767%	$197.6865	$197.69	$197.70	$197.70
Purchase #6	$249.87	6.804%	$266.8712	$266.87	$266.85	$266.90
Purchase #7	$102.79	13.672%	$116.8434	$116.84	$116.85	$116.80
7 purchase totals =	$1,171.74		$1,250.0802	$1,250.08	$1,250.05	$1,250.20