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	$186.81	5.200%	$196.5241	$196.52	$196.50	$196.50
Purchase #2	$191.41	3.833%	$198.7467	$198.75	$198.75	$198.70
Purchase #3	$43.81	9.378%	$47.9185	$47.92	$47.90	$47.90
Purchase #4	$73.95	6.576%	$78.813	$78.81	$78.80	$78.80
Purchase #5	$18.67	3.836%	$19.3862	$19.39	$19.40	$19.40
Purchase #6	$13.83	9.667%	$15.1669	$15.17	$15.15	$15.20
Purchase #7	$61.53	5.366%	$64.8317	$64.83	$64.85	$64.80
7 purchase totals =	$590.01		$621.3871	$621.39	$621.35	$621.30