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	$213.90	9.154%	$233.4804	$233.48	$233.50	$233.50
Purchase #2	$225.63	7.167%	$241.8009	$241.80	$241.80	$241.80
Purchase #3	$89.52	3.697%	$92.8296	$92.83	$92.85	$92.80
Purchase #4	$82.59	12.606%	$93.0013	$93.00	$93.00	$93.00
Purchase #5	$172.52	4.491%	$180.2679	$180.27	$180.25	$180.30
Purchase #6	$18.69	7.525%	$20.0964	$20.10	$20.10	$20.10
Purchase #7	$191.95	3.455%	$198.5819	$198.58	$198.60	$198.60
7 purchase totals =	$994.80		$1,060.0584	$1,060.06	$1,060.10	$1,060.10