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	$53.92	12.797%	$60.8201	$60.82	$60.80	$60.80
Purchase #2	$107.28	9.774%	$117.7655	$117.77	$117.75	$117.80
Purchase #3	$167.93	9.691%	$184.2041	$184.20	$184.20	$184.20
Purchase #4	$74.75	10.248%	$82.4104	$82.41	$82.40	$82.40
Purchase #5	$111.83	4.371%	$116.7181	$116.72	$116.70	$116.70
Purchase #6	$229.48	10.499%	$253.5731	$253.57	$253.55	$253.60
Purchase #7	$170.52	10.525%	$188.4672	$188.47	$188.45	$188.50
7 purchase totals =	$915.71		$1,003.9585	$1,003.96	$1,003.85	$1,004.00