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	$195.96	13.433%	$222.2833	$222.28	$222.30	$222.30
Purchase #2	$17.93	4.162%	$18.6762	$18.68	$18.70	$18.70
Purchase #3	$69.27	7.384%	$74.3849	$74.38	$74.40	$74.40
Purchase #4	$108.92	13.476%	$123.5981	$123.60	$123.60	$123.60
Purchase #5	$25.47	7.518%	$27.3848	$27.38	$27.40	$27.40
Purchase #6	$227.88	11.274%	$253.5712	$253.57	$253.55	$253.60
Purchase #7	$80.87	12.379%	$90.8809	$90.88	$90.90	$90.90
7 purchase totals =	$726.30		$810.7794	$810.77	$810.85	$810.90