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	$106.63	13.857%	$121.4057	$121.41	$121.40	$121.40
Purchase #2	$100.45	5.372%	$105.8462	$105.85	$105.85	$105.80
Purchase #3	$156.77	5.456%	$165.3234	$165.32	$165.30	$165.30
Purchase #4	$66.61	7.826%	$71.8229	$71.82	$71.80	$71.80
Purchase #5	$239.92	3.814%	$249.0705	$249.07	$249.05	$249.10
Purchase #6	$65.62	12.161%	$73.6	$73.60	$73.60	$73.60
Purchase #7	$200.52	11.397%	$223.3733	$223.37	$223.35	$223.40
7 purchase totals =	$936.52		$1,010.4420	$1,010.44	$1,010.35	$1,010.40