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	$206.37	3.585%	$213.7684	$213.77	$213.75	$213.80
Purchase #2	$57.93	8.535%	$62.8743	$62.87	$62.85	$62.90
Purchase #3	$19.82	8.532%	$21.511	$21.51	$21.50	$21.50
Purchase #4	$105.32	13.234%	$119.258	$119.26	$119.25	$119.30
Purchase #5	$42.87	7.244%	$45.9755	$45.98	$46.00	$46.00
Purchase #6	$167.90	4.392%	$175.2742	$175.27	$175.25	$175.30
Purchase #7	$10.60	7.158%	$11.3587	$11.36	$11.35	$11.40
7 purchase totals =	$610.81		$650.0201	$650.02	$649.95	$650.20