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	$30.58	5.795%	$32.3521	$32.35	$32.35	$32.40
Purchase #2	$63.40	3.264%	$65.4694	$65.47	$65.45	$65.50
Purchase #3	$171.53	11.754%	$191.6916	$191.69	$191.70	$191.70
Purchase #4	$12.53	5.314%	$13.1958	$13.20	$13.20	$13.20
Purchase #5	$70.39	3.426%	$72.8016	$72.80	$72.80	$72.80
Purchase #6	$147.97	11.551%	$165.062	$165.06	$165.05	$165.10
Purchase #7	$102.99	11.169%	$114.493	$114.49	$114.50	$114.50
7 purchase totals =	$599.39		$655.0655	$655.06	$655.05	$655.20