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	$58.72	5.323%	$61.8457	$61.85	$61.85	$61.80
Purchase #2	$37.55	12.519%	$42.2509	$42.25	$42.25	$42.30
Purchase #3	$191.75	10.493%	$211.8703	$211.87	$211.85	$211.90
Purchase #4	$212.85	7.691%	$229.2203	$229.22	$229.20	$229.20
Purchase #5	$62.87	4.737%	$65.8482	$65.85	$65.85	$65.80
Purchase #6	$118.53	5.527%	$125.0812	$125.08	$125.10	$125.10
Purchase #7	$178.59	7.231%	$191.5038	$191.50	$191.50	$191.50
7 purchase totals =	$860.86		$927.6204	$927.62	$927.60	$927.60