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	$57.89	3.350%	$59.8293	$59.83	$59.85	$59.80
Purchase #2	$28.66	5.267%	$30.1695	$30.17	$30.15	$30.20
Purchase #3	$223.32	13.131%	$252.6441	$252.64	$252.65	$252.60
Purchase #4	$37.63	9.506%	$41.2071	$41.21	$41.20	$41.20
Purchase #5	$152.64	10.652%	$168.8992	$168.90	$168.90	$168.90
Purchase #6	$8.52	3.293%	$8.8006	$8.80	$8.80	$8.80
Purchase #7	$180.82	8.861%	$196.8425	$196.84	$196.85	$196.80
7 purchase totals =	$689.48		$758.3923	$758.39	$758.40	$758.30