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	$40.44	12.697%	$45.5747	$45.57	$45.55	$45.60
Purchase #2	$46.37	4.155%	$48.2967	$48.30	$48.30	$48.30
Purchase #3	$70.36	9.409%	$76.9802	$76.98	$77.00	$77.00
Purchase #4	$101.57	10.634%	$112.371	$112.37	$112.35	$112.40
Purchase #5	$85.59	9.382%	$93.6201	$93.62	$93.60	$93.60
Purchase #6	$28.49	7.360%	$30.5869	$30.59	$30.60	$30.60
Purchase #7	$250.96	3.716%	$260.2857	$260.29	$260.30	$260.30
7 purchase totals =	$623.78		$667.7153	$667.72	$667.70	$667.80