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	$98.73	4.768%	$103.4374	$103.44	$103.45	$103.40
Purchase #2	$59.27	6.315%	$63.0129	$63.01	$63.00	$63.00
Purchase #3	$54.60	12.845%	$61.6134	$61.61	$61.60	$61.60
Purchase #4	$94.63	5.128%	$99.4826	$99.48	$99.50	$99.50
Purchase #5	$16.72	10.393%	$18.4577	$18.46	$18.45	$18.50
Purchase #6	$144.29	10.315%	$159.1735	$159.17	$159.15	$159.20
Purchase #7	$196.73	13.304%	$222.903	$222.90	$222.90	$222.90
7 purchase totals =	$664.97		$728.0805	$728.07	$728.05	$728.10