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	$220.57	10.191%	$243.0483	$243.05	$243.05	$243.00
Purchase #2	$98.77	13.261%	$111.8679	$111.87	$111.85	$111.90
Purchase #3	$59.89	4.158%	$62.3802	$62.38	$62.40	$62.40
Purchase #4	$100.54	8.430%	$109.0155	$109.02	$109.00	$109.00
Purchase #5	$45.31	3.763%	$47.015	$47.02	$47.00	$47.00
Purchase #6	$119.25	13.602%	$135.4704	$135.47	$135.45	$135.50
Purchase #7	$219.83	8.300%	$238.0759	$238.08	$238.10	$238.10
7 purchase totals =	$864.16		$946.8732	$946.89	$946.85	$946.90