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	$235.53	10.365%	$259.9427	$259.94	$259.95	$259.90
Purchase #2	$157.49	5.421%	$166.0275	$166.03	$166.05	$166.00
Purchase #3	$55.26	4.737%	$57.8777	$57.88	$57.90	$57.90
Purchase #4	$248.53	13.126%	$281.152	$281.15	$281.15	$281.20
Purchase #5	$163.55	13.508%	$185.6423	$185.64	$185.65	$185.60
Purchase #6	$98.71	4.872%	$103.5192	$103.52	$103.50	$103.50
Purchase #7	$47.27	7.616%	$50.8701	$50.87	$50.85	$50.90
7 purchase totals =	$1,006.34		$1,105.0315	$1,105.03	$1,105.05	$1,105.00