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	$75.55	9.575%	$82.7839	$82.78	$82.80	$82.80
Purchase #2	$83.85	4.820%	$87.8916	$87.89	$87.90	$87.90
Purchase #3	$61.49	5.633%	$64.9537	$64.95	$64.95	$65.00
Purchase #4	$167.33	10.508%	$184.913	$184.91	$184.90	$184.90
Purchase #5	$84.42	6.633%	$90.0196	$90.02	$90.00	$90.00
Purchase #6	$102.41	6.102%	$108.6591	$108.66	$108.65	$108.70
Purchase #7	$81.42	6.690%	$86.867	$86.87	$86.85	$86.90
7 purchase totals =	$656.47		$706.0879	$706.08	$706.05	$706.20