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	$87.55	10.298%	$96.5659	$96.57	$96.55	$96.60
Purchase #2	$211.39	7.669%	$227.6015	$227.60	$227.60	$227.60
Purchase #3	$242.72	11.612%	$270.9046	$270.90	$270.90	$270.90
Purchase #4	$35.39	11.726%	$39.5398	$39.54	$39.55	$39.50
Purchase #5	$94.54	6.551%	$100.7333	$100.73	$100.75	$100.70
Purchase #6	$152.49	10.762%	$168.901	$168.90	$168.90	$168.90
Purchase #7	$51.57	7.170%	$55.2676	$55.27	$55.25	$55.30
7 purchase totals =	$875.65		$959.5137	$959.51	$959.50	$959.50