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	$137.90	10.429%	$152.2816	$152.28	$152.30	$152.30
Purchase #2	$52.41	4.822%	$54.9372	$54.94	$54.95	$54.90
Purchase #3	$19.95	9.196%	$21.7846	$21.78	$21.80	$21.80
Purchase #4	$102.84	10.712%	$113.8562	$113.86	$113.85	$113.90
Purchase #5	$237.78	7.392%	$255.3567	$255.36	$255.35	$255.40
Purchase #6	$61.50	11.522%	$68.586	$68.59	$68.60	$68.60
Purchase #7	$170.56	7.228%	$182.8881	$182.89	$182.90	$182.90
7 purchase totals =	$782.94		$849.6904	$849.70	$849.75	$849.80