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	$85.56	4.710%	$89.5899	$89.59	$89.60	$89.60
Purchase #2	$202.84	7.348%	$217.7447	$217.74	$217.75	$217.70
Purchase #3	$107.35	8.513%	$116.4887	$116.49	$116.50	$116.50
Purchase #4	$240.55	10.671%	$266.2191	$266.22	$266.20	$266.20
Purchase #5	$161.56	4.334%	$168.562	$168.56	$168.55	$168.60
Purchase #6	$68.55	7.655%	$73.7975	$73.80	$73.80	$73.80
Purchase #7	$62.61	13.276%	$70.9221	$70.92	$70.90	$70.90
7 purchase totals =	$929.02		$1,003.3240	$1,003.32	$1,003.30	$1,003.30