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	$180.97	10.753%	$200.4297	$200.43	$200.45	$200.40
Purchase #2	$99.63	9.692%	$109.2861	$109.29	$109.30	$109.30
Purchase #3	$200.61	12.214%	$225.1125	$225.11	$225.10	$225.10
Purchase #4	$67.60	10.648%	$74.798	$74.80	$74.80	$74.80
Purchase #5	$242.58	12.419%	$272.706	$272.71	$272.70	$272.70
Purchase #6	$62.45	8.232%	$67.5909	$67.59	$67.60	$67.60
Purchase #7	$227.46	12.348%	$255.5468	$255.55	$255.55	$255.50
7 purchase totals =	$1,081.30		$1,205.4700	$1,205.48	$1,205.50	$1,205.40