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	$192.33	13.628%	$218.5407	$218.54	$218.55	$218.50
Purchase #2	$80.86	3.651%	$83.8122	$83.81	$83.80	$83.80
Purchase #3	$171.74	8.816%	$186.8806	$186.88	$186.90	$186.90
Purchase #4	$46.43	3.340%	$47.9808	$47.98	$48.00	$48.00
Purchase #5	$148.86	5.550%	$157.1217	$157.12	$157.10	$157.10
Purchase #6	$142.59	6.255%	$151.509	$151.51	$151.50	$151.50
Purchase #7	$182.89	13.735%	$208.0099	$208.01	$208.00	$208.00
7 purchase totals =	$965.70		$1,053.8549	$1,053.85	$1,053.85	$1,053.80