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	$152.46	13.165%	$172.5314	$172.53	$172.55	$172.50
Purchase #2	$110.49	3.283%	$114.1174	$114.12	$114.10	$114.10
Purchase #3	$38.54	8.380%	$41.7697	$41.77	$41.75	$41.80
Purchase #4	$52.46	10.379%	$57.9048	$57.90	$57.90	$57.90
Purchase #5	$48.26	5.842%	$51.0793	$51.08	$51.10	$51.10
Purchase #6	$162.39	10.835%	$179.985	$179.99	$180.00	$180.00
Purchase #7	$59.32	4.689%	$62.1015	$62.10	$62.10	$62.10
7 purchase totals =	$623.92		$679.4891	$679.49	$679.50	$679.50