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	$203.89	3.621%	$211.2729	$211.27	$211.25	$211.30
Purchase #2	$162.86	3.421%	$168.4314	$168.43	$168.45	$168.40
Purchase #3	$193.83	3.283%	$200.1934	$200.19	$200.20	$200.20
Purchase #4	$22.85	13.624%	$25.9631	$25.96	$25.95	$26.00
Purchase #5	$196.90	4.412%	$205.5872	$205.59	$205.60	$205.60
Purchase #6	$54.30	3.424%	$56.1592	$56.16	$56.15	$56.20
Purchase #7	$110.78	11.836%	$123.8919	$123.89	$123.90	$123.90
7 purchase totals =	$945.41		$991.4991	$991.49	$991.50	$991.60