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	$190.55	13.164%	$215.634	$215.63	$215.65	$215.60
Purchase #2	$152.71	7.590%	$164.3007	$164.30	$164.30	$164.30
Purchase #3	$61.54	9.848%	$67.6005	$67.60	$67.60	$67.60
Purchase #4	$113.83	5.105%	$119.641	$119.64	$119.65	$119.60
Purchase #5	$94.47	3.416%	$97.6971	$97.70	$97.70	$97.70
Purchase #6	$56.52	9.334%	$61.7956	$61.80	$61.80	$61.80
Purchase #7	$62.77	13.669%	$71.35	$71.35	$71.35	$71.40
7 purchase totals =	$732.39		$798.0189	$798.02	$798.05	$798.00