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	$43.36	13.833%	$49.358	$49.36	$49.35	$49.40
Purchase #2	$191.44	13.785%	$217.83	$217.83	$217.85	$217.80
Purchase #3	$190.81	10.166%	$210.2077	$210.21	$210.20	$210.20
Purchase #4	$206.33	13.155%	$233.4727	$233.47	$233.45	$233.50
Purchase #5	$142.96	10.778%	$158.3682	$158.37	$158.35	$158.40
Purchase #6	$63.83	13.507%	$72.4515	$72.45	$72.45	$72.50
Purchase #7	$90.95	6.450%	$96.8163	$96.82	$96.80	$96.80
7 purchase totals =	$929.68		$1,038.5044	$1,038.51	$1,038.45	$1,038.60