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	$170.59	12.190%	$191.3849	$191.38	$191.40	$191.40
Purchase #2	$159.94	10.444%	$176.6441	$176.64	$176.65	$176.60
Purchase #3	$146.64	10.381%	$161.8627	$161.86	$161.85	$161.90
Purchase #4	$97.46	3.289%	$100.6655	$100.67	$100.65	$100.70
Purchase #5	$52.58	7.124%	$56.3258	$56.33	$56.35	$56.30
Purchase #6	$176.65	6.724%	$188.5279	$188.53	$188.55	$188.50
Purchase #7	$208.43	4.770%	$218.3721	$218.37	$218.35	$218.40
7 purchase totals =	$1,012.29		$1,093.7830	$1,093.78	$1,093.80	$1,093.80