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	$166.79	11.284%	$185.6106	$185.61	$185.60	$185.60
Purchase #2	$45.37	13.614%	$51.5467	$51.55	$51.55	$51.50
Purchase #3	$93.89	12.109%	$105.2591	$105.26	$105.25	$105.30
Purchase #4	$138.89	6.383%	$147.7553	$147.76	$147.75	$147.80
Purchase #5	$129.64	5.359%	$136.5874	$136.59	$136.60	$136.60
Purchase #6	$87.93	11.144%	$97.7289	$97.73	$97.75	$97.70
Purchase #7	$168.96	4.627%	$176.7778	$176.78	$176.80	$176.80
7 purchase totals =	$831.47		$901.2658	$901.28	$901.30	$901.30