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	4.476%	$199.079	$199.08	$199.10	$199.10
Purchase #2	$39.83	12.436%	$44.7833	$44.78	$44.80	$44.80
Purchase #3	$112.54	9.863%	$123.6398	$123.64	$123.65	$123.60
Purchase #4	$40.87	9.508%	$44.7559	$44.76	$44.75	$44.80
Purchase #5	$131.54	10.407%	$145.2294	$145.23	$145.25	$145.20
Purchase #6	$94.46	8.486%	$102.4759	$102.48	$102.50	$102.50
Purchase #7	$6.83	7.649%	$7.3524	$7.35	$7.35	$7.40
7 purchase totals =	$616.62		$667.3157	$667.32	$667.40	$667.40