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	$208.81	11.261%	$232.3241	$232.32	$232.30	$232.30
Purchase #2	$104.92	7.301%	$112.5802	$112.58	$112.60	$112.60
Purchase #3	$224.72	8.368%	$243.5246	$243.52	$243.50	$243.50
Purchase #4	$88.98	4.475%	$92.9619	$92.96	$92.95	$93.00
Purchase #5	$73.65	4.303%	$76.8192	$76.82	$76.80	$76.80
Purchase #6	$204.99	5.303%	$215.8606	$215.86	$215.85	$215.90
Purchase #7	$86.81	3.228%	$89.6122	$89.61	$89.60	$89.60
7 purchase totals =	$992.88		$1,063.6828	$1,063.67	$1,063.60	$1,063.70