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	$12.93	4.144%	$13.4658	$13.47	$13.45	$13.50
Purchase #2	$16.80	9.497%	$18.3955	$18.40	$18.40	$18.40
Purchase #3	$87.56	12.500%	$98.505	$98.51	$98.50	$98.50
Purchase #4	$233.98	9.704%	$256.6854	$256.69	$256.70	$256.70
Purchase #5	$82.64	3.585%	$85.6026	$85.60	$85.60	$85.60
Purchase #6	$218.73	11.315%	$243.4793	$243.48	$243.50	$243.50
Purchase #7	$18.65	5.609%	$19.6961	$19.70	$19.70	$19.70
7 purchase totals =	$671.29		$735.8297	$735.85	$735.85	$735.90