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	$100.63	8.787%	$109.4724	$109.47	$109.45	$109.50
Purchase #2	$75.89	6.196%	$80.5921	$80.59	$80.60	$80.60
Purchase #3	$199.83	9.307%	$218.4282	$218.43	$218.45	$218.40
Purchase #4	$248.30	6.759%	$265.0826	$265.08	$265.10	$265.10
Purchase #5	$25.45	9.452%	$27.8555	$27.86	$27.85	$27.90
Purchase #6	$138.45	9.482%	$151.5778	$151.58	$151.60	$151.60
Purchase #7	$81.63	8.334%	$88.433	$88.43	$88.45	$88.40
7 purchase totals =	$870.18		$941.4416	$941.44	$941.50	$941.50