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	$202.48	10.269%	$223.2727	$223.27	$223.25	$223.30
Purchase #2	$157.53	11.605%	$175.8114	$175.81	$175.80	$175.80
Purchase #3	$76.75	7.127%	$82.22	$82.22	$82.20	$82.20
Purchase #4	$149.77	5.684%	$158.2829	$158.28	$158.30	$158.30
Purchase #5	$40.74	6.808%	$43.5136	$43.51	$43.50	$43.50
Purchase #6	$188.42	8.256%	$203.976	$203.98	$204.00	$204.00
Purchase #7	$151.72	8.292%	$164.3006	$164.30	$164.30	$164.30
7 purchase totals =	$967.41		$1,051.3772	$1,051.37	$1,051.35	$1,051.40