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	$103.88	7.868%	$112.0533	$112.05	$112.05	$112.10
Purchase #2	$193.50	13.108%	$218.864	$218.86	$218.85	$218.90
Purchase #3	$172.70	13.546%	$196.0939	$196.09	$196.10	$196.10
Purchase #4	$131.55	10.255%	$145.0405	$145.04	$145.05	$145.00
Purchase #5	$76.61	7.821%	$82.6017	$82.60	$82.60	$82.60
Purchase #6	$28.89	5.300%	$30.4212	$30.42	$30.40	$30.40
Purchase #7	$215.81	12.728%	$243.2783	$243.28	$243.30	$243.30
7 purchase totals =	$922.94		$1,028.3529	$1,028.34	$1,028.35	$1,028.40