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	$237.49	9.638%	$260.3793	$260.38	$260.40	$260.40
Purchase #2	$94.99	4.340%	$99.1126	$99.11	$99.10	$99.10
Purchase #3	$34.38	7.726%	$37.0362	$37.04	$37.05	$37.00
Purchase #4	$192.40	11.600%	$214.7184	$214.72	$214.70	$214.70
Purchase #5	$116.63	8.872%	$126.9774	$126.98	$127.00	$127.00
Purchase #6	$201.89	11.588%	$225.285	$225.29	$225.30	$225.30
Purchase #7	$111.98	13.565%	$127.1701	$127.17	$127.15	$127.20
7 purchase totals =	$989.76		$1,090.6790	$1,090.69	$1,090.70	$1,090.70