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	$72.52	8.477%	$78.6675	$78.67	$78.65	$78.70
Purchase #2	$241.86	12.616%	$272.3731	$272.37	$272.35	$272.40
Purchase #3	$122.83	13.514%	$139.4292	$139.43	$139.45	$139.40
Purchase #4	$122.77	6.745%	$131.0508	$131.05	$131.05	$131.10
Purchase #5	$222.42	7.245%	$238.5343	$238.53	$238.55	$238.50
Purchase #6	$156.73	5.389%	$165.1762	$165.18	$165.20	$165.20
Purchase #7	$30.90	13.511%	$35.0749	$35.07	$35.05	$35.10
7 purchase totals =	$970.03		$1,060.3060	$1,060.30	$1,060.30	$1,060.40