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	$183.92	7.176%	$197.1181	$197.12	$197.10	$197.10
Purchase #2	$59.84	13.490%	$67.9124	$67.91	$67.90	$67.90
Purchase #3	$57.42	8.789%	$62.4666	$62.47	$62.45	$62.50
Purchase #4	$15.57	8.620%	$16.9121	$16.91	$16.90	$16.90
Purchase #5	$228.29	5.375%	$240.5606	$240.56	$240.55	$240.60
Purchase #6	$44.66	12.557%	$50.268	$50.27	$50.25	$50.30
Purchase #7	$98.72	4.826%	$103.4842	$103.48	$103.50	$103.50
7 purchase totals =	$688.42		$738.7220	$738.72	$738.65	$738.80