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	$84.94	10.667%	$94.0005	$94.00	$94.00	$94.00
Purchase #2	$100.50	13.496%	$114.0635	$114.06	$114.05	$114.10
Purchase #3	$91.60	11.306%	$101.9563	$101.96	$101.95	$102.00
Purchase #4	$31.77	9.292%	$34.7221	$34.72	$34.70	$34.70
Purchase #5	$98.36	13.451%	$111.5904	$111.59	$111.60	$111.60
Purchase #6	$77.88	7.300%	$83.5652	$83.57	$83.55	$83.60
Purchase #7	$105.76	3.291%	$109.2406	$109.24	$109.25	$109.20
7 purchase totals =	$590.81		$649.1386	$649.14	$649.10	$649.20