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	$162.53	12.264%	$182.4627	$182.46	$182.45	$182.50
Purchase #2	$164.31	12.152%	$184.277	$184.28	$184.30	$184.30
Purchase #3	$122.37	5.849%	$129.5274	$129.53	$129.55	$129.50
Purchase #4	$182.38	4.680%	$190.9154	$190.92	$190.90	$190.90
Purchase #5	$175.94	3.508%	$182.112	$182.11	$182.10	$182.10
Purchase #6	$13.87	10.492%	$15.3252	$15.33	$15.35	$15.30
Purchase #7	$175.80	3.143%	$181.3254	$181.33	$181.35	$181.30
7 purchase totals =	$997.20		$1,065.9451	$1,065.96	$1,066.00	$1,065.90