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	$96.32	7.544%	$103.5864	$103.59	$103.60	$103.60
Purchase #2	$27.46	4.750%	$28.7644	$28.76	$28.75	$28.80
Purchase #3	$101.35	13.440%	$114.9714	$114.97	$114.95	$115.00
Purchase #4	$105.59	13.669%	$120.0231	$120.02	$120.00	$120.00
Purchase #5	$178.39	10.330%	$196.8177	$196.82	$196.80	$196.80
Purchase #6	$82.31	6.306%	$87.5005	$87.50	$87.50	$87.50
Purchase #7	$102.38	5.434%	$107.9433	$107.94	$107.95	$107.90
7 purchase totals =	$693.80		$759.6068	$759.60	$759.55	$759.60