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	$150.25	10.536%	$166.0803	$166.08	$166.10	$166.10
Purchase #2	$158.83	7.257%	$170.3563	$170.36	$170.35	$170.40
Purchase #3	$139.88	8.255%	$151.4271	$151.43	$151.45	$151.40
Purchase #4	$19.31	7.592%	$20.776	$20.78	$20.80	$20.80
Purchase #5	$202.26	12.400%	$227.3402	$227.34	$227.35	$227.30
Purchase #6	$244.55	8.305%	$264.8599	$264.86	$264.85	$264.90
Purchase #7	$151.50	8.275%	$164.0366	$164.04	$164.05	$164.00
7 purchase totals =	$1,066.58		$1,164.8764	$1,164.89	$1,164.95	$1,164.90