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	$47.39	8.716%	$51.5205	$51.52	$51.50	$51.50
Purchase #2	$14.48	5.861%	$15.3287	$15.33	$15.35	$15.30
Purchase #3	$153.37	5.851%	$162.3437	$162.34	$162.35	$162.30
Purchase #4	$200.44	11.702%	$223.8955	$223.90	$223.90	$223.90
Purchase #5	$107.85	5.264%	$113.5272	$113.53	$113.55	$113.50
Purchase #6	$6.68	6.346%	$7.1039	$7.10	$7.10	$7.10
Purchase #7	$137.25	11.334%	$152.8059	$152.81	$152.80	$152.80
7 purchase totals =	$667.46		$726.5254	$726.53	$726.55	$726.40