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	$115.56	11.160%	$128.4565	$128.46	$128.45	$128.50
Purchase #2	$133.62	5.788%	$141.3539	$141.35	$141.35	$141.40
Purchase #3	$85.46	12.834%	$96.4279	$96.43	$96.45	$96.40
Purchase #4	$151.51	7.518%	$162.9005	$162.90	$162.90	$162.90
Purchase #5	$204.48	6.827%	$218.4398	$218.44	$218.45	$218.40
Purchase #6	$75.92	4.624%	$79.4305	$79.43	$79.45	$79.40
Purchase #7	$30.28	11.862%	$33.8718	$33.87	$33.85	$33.90
7 purchase totals =	$796.83		$860.8809	$860.88	$860.90	$860.90