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	$158.27	9.489%	$173.2882	$173.29	$173.30	$173.30
Purchase #2	$114.60	12.471%	$128.8918	$128.89	$128.90	$128.90
Purchase #3	$139.38	7.787%	$150.2335	$150.23	$150.25	$150.20
Purchase #4	$36.43	7.217%	$39.0592	$39.06	$39.05	$39.10
Purchase #5	$238.47	7.483%	$256.3147	$256.31	$256.30	$256.30
Purchase #6	$246.59	5.436%	$259.9946	$259.99	$260.00	$260.00
Purchase #7	$13.65	6.625%	$14.5543	$14.55	$14.55	$14.60
7 purchase totals =	$947.39		$1,022.3363	$1,022.32	$1,022.35	$1,022.40