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	$81.44	10.344%	$89.8642	$89.86	$89.85	$89.90
Purchase #2	$168.52	13.442%	$191.1725	$191.17	$191.15	$191.20
Purchase #3	$119.92	8.723%	$130.3806	$130.38	$130.40	$130.40
Purchase #4	$5.55	6.530%	$5.9124	$5.91	$5.90	$5.90
Purchase #5	$175.83	8.623%	$190.9918	$190.99	$191.00	$191.00
Purchase #6	$181.89	12.724%	$205.0337	$205.03	$205.05	$205.00
Purchase #7	$211.32	7.694%	$227.579	$227.58	$227.60	$227.60
7 purchase totals =	$944.47		$1,040.9342	$1,040.92	$1,040.95	$1,041.00