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	$45.78	10.564%	$50.6162	$50.62	$50.60	$50.60
Purchase #2	$63.48	4.403%	$66.275	$66.28	$66.30	$66.30
Purchase #3	$181.61	12.830%	$204.9106	$204.91	$204.90	$204.90
Purchase #4	$104.63	13.106%	$118.3428	$118.34	$118.35	$118.30
Purchase #5	$207.54	5.121%	$218.1681	$218.17	$218.15	$218.20
Purchase #6	$203.60	9.397%	$222.7323	$222.73	$222.75	$222.70
Purchase #7	$31.89	13.572%	$36.2181	$36.22	$36.20	$36.20
7 purchase totals =	$838.53		$917.2631	$917.27	$917.25	$917.20