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	$88.47	4.596%	$92.5361	$92.54	$92.55	$92.50
Purchase #2	$158.76	4.430%	$165.7931	$165.79	$165.80	$165.80
Purchase #3	$166.76	12.620%	$187.8051	$187.81	$187.80	$187.80
Purchase #4	$239.71	7.847%	$258.52	$258.52	$258.50	$258.50
Purchase #5	$111.28	5.480%	$117.3781	$117.38	$117.40	$117.40
Purchase #6	$46.38	4.724%	$48.571	$48.57	$48.55	$48.60
Purchase #7	$189.75	5.801%	$200.7574	$200.76	$200.75	$200.80
7 purchase totals =	$1,001.11		$1,071.3608	$1,071.37	$1,071.35	$1,071.40