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	$184.61	3.398%	$190.883	$190.88	$190.90	$190.90
Purchase #2	$148.63	10.690%	$164.5185	$164.52	$164.50	$164.50
Purchase #3	$250.46	10.145%	$275.8692	$275.87	$275.85	$275.90
Purchase #4	$210.67	3.761%	$218.5933	$218.59	$218.60	$218.60
Purchase #5	$123.70	10.334%	$136.4832	$136.48	$136.50	$136.50
Purchase #6	$52.29	12.495%	$58.8236	$58.82	$58.80	$58.80
Purchase #7	$11.33	6.663%	$12.0849	$12.08	$12.10	$12.10
7 purchase totals =	$981.69		$1,057.2557	$1,057.24	$1,057.25	$1,057.30