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	$96.32	8.247%	$104.2635	$104.26	$104.25	$104.30
Purchase #2	$156.90	9.718%	$172.1475	$172.15	$172.15	$172.10
Purchase #3	$90.37	3.455%	$93.4923	$93.49	$93.50	$93.50
Purchase #4	$209.38	8.378%	$226.9219	$226.92	$226.90	$226.90
Purchase #5	$245.89	10.396%	$271.4527	$271.45	$271.45	$271.50
Purchase #6	$48.72	7.120%	$52.1889	$52.19	$52.20	$52.20
Purchase #7	$114.48	4.298%	$119.4004	$119.40	$119.40	$119.40
7 purchase totals =	$962.06		$1,039.8672	$1,039.86	$1,039.85	$1,039.90