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	$248.87	9.565%	$272.6744	$272.67	$272.65	$272.70
Purchase #2	$249.83	11.822%	$279.3649	$279.36	$279.35	$279.40
Purchase #3	$212.98	7.331%	$228.5936	$228.59	$228.60	$228.60
Purchase #4	$142.86	10.521%	$157.8903	$157.89	$157.90	$157.90
Purchase #5	$83.25	10.269%	$91.7989	$91.80	$91.80	$91.80
Purchase #6	$82.43	7.769%	$88.834	$88.83	$88.85	$88.80
Purchase #7	$64.39	3.330%	$66.5342	$66.53	$66.55	$66.50
7 purchase totals =	$1,084.61		$1,185.6903	$1,185.67	$1,185.70	$1,185.70