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	$135.28	11.542%	$150.894	$150.89	$150.90	$150.90
Purchase #2	$118.93	10.349%	$131.2381	$131.24	$131.25	$131.20
Purchase #3	$172.98	3.321%	$178.7247	$178.72	$178.70	$178.70
Purchase #4	$115.85	9.807%	$127.2114	$127.21	$127.20	$127.20
Purchase #5	$245.33	3.337%	$253.5167	$253.52	$253.50	$253.50
Purchase #6	$146.29	12.690%	$164.8542	$164.85	$164.85	$164.90
Purchase #7	$139.56	8.638%	$151.6152	$151.62	$151.60	$151.60
7 purchase totals =	$1,074.22		$1,158.0543	$1,158.05	$1,158.00	$1,158.00