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	$156.58	3.799%	$162.5285	$162.53	$162.55	$162.50
Purchase #2	$50.94	13.492%	$57.8128	$57.81	$57.80	$57.80
Purchase #3	$103.46	6.179%	$109.8528	$109.85	$109.85	$109.90
Purchase #4	$111.87	7.597%	$120.3688	$120.37	$120.35	$120.40
Purchase #5	$17.53	7.590%	$18.8605	$18.86	$18.85	$18.90
Purchase #6	$198.92	5.521%	$209.9024	$209.90	$209.90	$209.90
Purchase #7	$33.62	3.801%	$34.8979	$34.90	$34.90	$34.90
7 purchase totals =	$672.92		$714.2237	$714.22	$714.20	$714.30