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	$234.56	7.796%	$252.8463	$252.85	$252.85	$252.80
Purchase #2	$117.71	9.319%	$128.6794	$128.68	$128.70	$128.70
Purchase #3	$127.35	12.105%	$142.7657	$142.77	$142.75	$142.80
Purchase #4	$199.30	9.740%	$218.7118	$218.71	$218.70	$218.70
Purchase #5	$178.91	6.424%	$190.4032	$190.40	$190.40	$190.40
Purchase #6	$148.58	11.453%	$165.5969	$165.60	$165.60	$165.60
Purchase #7	$61.62	6.868%	$65.8521	$65.85	$65.85	$65.90
7 purchase totals =	$1,068.03		$1,164.8554	$1,164.86	$1,164.85	$1,164.90