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	$17.32	3.617%	$17.9465	$17.95	$17.95	$17.90
Purchase #2	$236.60	9.633%	$259.3917	$259.39	$259.40	$259.40
Purchase #3	$85.41	4.586%	$89.3269	$89.33	$89.35	$89.30
Purchase #4	$151.63	10.338%	$167.3055	$167.31	$167.30	$167.30
Purchase #5	$221.61	12.821%	$250.0226	$250.02	$250.00	$250.00
Purchase #6	$199.51	9.743%	$218.9483	$218.95	$218.95	$218.90
Purchase #7	$62.61	6.197%	$66.4899	$66.49	$66.50	$66.50
7 purchase totals =	$974.69		$1,069.4314	$1,069.44	$1,069.45	$1,069.30