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	$175.93	5.394%	$185.4197	$185.42	$185.40	$185.40
Purchase #2	$40.29	10.562%	$44.5454	$44.55	$44.55	$44.50
Purchase #3	$128.25	5.121%	$134.8177	$134.82	$134.80	$134.80
Purchase #4	$64.54	13.232%	$73.0799	$73.08	$73.10	$73.10
Purchase #5	$95.61	4.831%	$100.2289	$100.23	$100.25	$100.20
Purchase #6	$63.48	13.260%	$71.8974	$71.90	$71.90	$71.90
Purchase #7	$131.74	11.527%	$146.9257	$146.93	$146.95	$146.90
7 purchase totals =	$699.84		$756.9147	$756.93	$756.95	$756.80