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	$84.68	7.294%	$90.8566	$90.86	$90.85	$90.90
Purchase #2	$194.69	7.387%	$209.0718	$209.07	$209.05	$209.10
Purchase #3	$170.30	5.590%	$179.8198	$179.82	$179.80	$179.80
Purchase #4	$234.47	13.162%	$265.3309	$265.33	$265.35	$265.30
Purchase #5	$160.88	11.605%	$179.5501	$179.55	$179.55	$179.60
Purchase #6	$58.97	8.543%	$64.0078	$64.01	$64.00	$64.00
Purchase #7	$142.72	4.301%	$148.8584	$148.86	$148.85	$148.90
7 purchase totals =	$1,046.71		$1,137.4954	$1,137.50	$1,137.45	$1,137.60