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	$220.33	13.621%	$250.3411	$250.34	$250.35	$250.30
Purchase #2	$15.47	3.840%	$16.064	$16.06	$16.05	$16.10
Purchase #3	$45.54	12.297%	$51.1401	$51.14	$51.15	$51.10
Purchase #4	$161.25	8.554%	$175.0433	$175.04	$175.05	$175.00
Purchase #5	$90.87	13.835%	$103.4419	$103.44	$103.45	$103.40
Purchase #6	$111.89	10.360%	$123.4818	$123.48	$123.50	$123.50
Purchase #7	$82.77	5.163%	$87.0434	$87.04	$87.05	$87.00
7 purchase totals =	$728.12		$806.5556	$806.54	$806.60	$806.40