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	$146.29	8.618%	$158.8973	$158.90	$158.90	$158.90
Purchase #2	$127.85	3.545%	$132.3823	$132.38	$132.40	$132.40
Purchase #3	$234.43	4.609%	$245.2349	$245.23	$245.25	$245.20
Purchase #4	$152.27	8.421%	$165.0927	$165.09	$165.10	$165.10
Purchase #5	$164.62	12.296%	$184.8617	$184.86	$184.85	$184.90
Purchase #6	$81.76	13.505%	$92.8017	$92.80	$92.80	$92.80
Purchase #7	$99.53	11.620%	$111.0954	$111.10	$111.10	$111.10
7 purchase totals =	$1,006.75		$1,090.3660	$1,090.36	$1,090.40	$1,090.40