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	$118.69	4.843%	$124.4382	$124.44	$124.45	$124.40
Purchase #2	$82.81	3.233%	$85.4872	$85.49	$85.50	$85.50
Purchase #3	$55.97	6.294%	$59.4928	$59.49	$59.50	$59.50
Purchase #4	$220.44	13.116%	$249.3529	$249.35	$249.35	$249.40
Purchase #5	$85.92	3.647%	$89.0535	$89.05	$89.05	$89.10
Purchase #6	$83.64	4.477%	$87.3846	$87.38	$87.40	$87.40
Purchase #7	$116.45	5.779%	$123.1796	$123.18	$123.20	$123.20
7 purchase totals =	$763.92		$818.3888	$818.38	$818.45	$818.50