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	$52.75	13.160%	$59.6919	$59.69	$59.70	$59.70
Purchase #2	$15.81	7.172%	$16.9439	$16.94	$16.95	$16.90
Purchase #3	$28.44	12.758%	$32.0684	$32.07	$32.05	$32.10
Purchase #4	$149.93	9.442%	$164.0864	$164.09	$164.10	$164.10
Purchase #5	$95.31	3.203%	$98.3628	$98.36	$98.35	$98.40
Purchase #6	$87.71	13.434%	$99.493	$99.49	$99.50	$99.50
Purchase #7	$166.34	6.264%	$176.7595	$176.76	$176.75	$176.80
7 purchase totals =	$596.29		$647.4059	$647.40	$647.40	$647.50