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	$61.34	9.259%	$67.0195	$67.02	$67.00	$67.00
Purchase #2	$168.66	3.396%	$174.3877	$174.39	$174.40	$174.40
Purchase #3	$157.67	5.732%	$166.7076	$166.71	$166.70	$166.70
Purchase #4	$185.39	6.820%	$198.0336	$198.03	$198.05	$198.00
Purchase #5	$132.65	3.858%	$137.7676	$137.77	$137.75	$137.80
Purchase #6	$85.94	3.642%	$89.0699	$89.07	$89.05	$89.10
Purchase #7	$102.31	3.111%	$105.4929	$105.49	$105.50	$105.50
7 purchase totals =	$893.96		$938.4788	$938.48	$938.45	$938.50