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	$175.33	8.708%	$190.5977	$190.60	$190.60	$190.60
Purchase #2	$118.88	12.385%	$133.6033	$133.60	$133.60	$133.60
Purchase #3	$63.67	13.675%	$72.3769	$72.38	$72.40	$72.40
Purchase #4	$188.42	6.227%	$200.1529	$200.15	$200.15	$200.20
Purchase #5	$100.99	8.811%	$109.8882	$109.89	$109.90	$109.90
Purchase #6	$30.40	5.709%	$32.1355	$32.14	$32.15	$32.10
Purchase #7	$27.51	9.257%	$30.0566	$30.06	$30.05	$30.10
7 purchase totals =	$705.20		$768.8111	$768.82	$768.85	$768.90