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	$145.79	5.274%	$153.479	$153.48	$153.50	$153.50
Purchase #2	$127.27	11.635%	$142.0779	$142.08	$142.10	$142.10
Purchase #3	$11.65	5.642%	$12.3073	$12.31	$12.30	$12.30
Purchase #4	$163.95	10.629%	$181.3762	$181.38	$181.40	$181.40
Purchase #5	$169.47	7.460%	$182.1125	$182.11	$182.10	$182.10
Purchase #6	$81.43	10.397%	$89.8963	$89.90	$89.90	$89.90
Purchase #7	$63.63	3.774%	$66.0314	$66.03	$66.05	$66.00
7 purchase totals =	$763.19		$827.2806	$827.29	$827.35	$827.30