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	$62.52	9.762%	$68.6232	$68.62	$68.60	$68.60
Purchase #2	$137.82	13.109%	$155.8868	$155.89	$155.90	$155.90
Purchase #3	$125.29	12.350%	$140.7633	$140.76	$140.75	$140.80
Purchase #4	$223.75	6.702%	$238.7457	$238.75	$238.75	$238.70
Purchase #5	$199.41	7.308%	$213.9829	$213.98	$214.00	$214.00
Purchase #6	$180.74	5.384%	$190.471	$190.47	$190.45	$190.50
Purchase #7	$80.93	5.711%	$85.5519	$85.55	$85.55	$85.60
7 purchase totals =	$1,010.46		$1,094.0248	$1,094.02	$1,094.00	$1,094.10