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	$238.72	8.504%	$259.0207	$259.02	$259.00	$259.00
Purchase #2	$65.56	10.704%	$72.5775	$72.58	$72.60	$72.60
Purchase #3	$107.43	4.474%	$112.2364	$112.24	$112.25	$112.20
Purchase #4	$196.36	13.226%	$222.3306	$222.33	$222.35	$222.30
Purchase #5	$159.87	4.779%	$167.5102	$167.51	$167.50	$167.50
Purchase #6	$72.77	12.862%	$82.1297	$82.13	$82.15	$82.10
Purchase #7	$110.25	8.412%	$119.5242	$119.52	$119.50	$119.50
7 purchase totals =	$950.96		$1,035.3293	$1,035.33	$1,035.35	$1,035.20