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	$18.32	3.421%	$18.9467	$18.95	$18.95	$18.90
Purchase #2	$61.64	3.496%	$63.7949	$63.79	$63.80	$63.80
Purchase #3	$186.39	5.628%	$196.88	$196.88	$196.90	$196.90
Purchase #4	$21.90	13.626%	$24.8841	$24.88	$24.90	$24.90
Purchase #5	$231.26	8.671%	$251.3126	$251.31	$251.30	$251.30
Purchase #6	$47.37	7.614%	$50.9768	$50.98	$51.00	$51.00
Purchase #7	$99.33	12.635%	$111.8803	$111.88	$111.90	$111.90
7 purchase totals =	$666.21		$718.6754	$718.67	$718.75	$718.70