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	$100.57	8.824%	$109.4443	$109.44	$109.45	$109.40
Purchase #2	$37.49	8.598%	$40.7134	$40.71	$40.70	$40.70
Purchase #3	$93.29	6.102%	$98.9826	$98.98	$99.00	$99.00
Purchase #4	$173.65	8.777%	$188.8913	$188.89	$188.90	$188.90
Purchase #5	$107.27	10.456%	$118.4862	$118.49	$118.50	$118.50
Purchase #6	$227.26	5.418%	$239.5729	$239.57	$239.55	$239.60
Purchase #7	$194.79	12.357%	$218.8602	$218.86	$218.85	$218.90
7 purchase totals =	$934.32		$1,014.9509	$1,014.94	$1,014.95	$1,015.00