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	$148.32	8.721%	$161.255	$161.26	$161.25	$161.30
Purchase #2	$94.38	4.426%	$98.5573	$98.56	$98.55	$98.60
Purchase #3	$92.72	7.678%	$99.839	$99.84	$99.85	$99.80
Purchase #4	$181.34	13.472%	$205.7701	$205.77	$205.75	$205.80
Purchase #5	$119.39	12.670%	$134.5167	$134.52	$134.50	$134.50
Purchase #6	$178.60	7.413%	$191.8396	$191.84	$191.85	$191.80
Purchase #7	$105.91	11.318%	$117.8969	$117.90	$117.90	$117.90
7 purchase totals =	$920.66		$1,009.6746	$1,009.69	$1,009.65	$1,009.70