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	$245.58	10.461%	$271.2701	$271.27	$271.25	$271.30
Purchase #2	$156.64	6.296%	$166.5021	$166.50	$166.50	$166.50
Purchase #3	$30.41	11.583%	$33.9324	$33.93	$33.95	$33.90
Purchase #4	$80.80	11.338%	$89.9611	$89.96	$89.95	$90.00
Purchase #5	$128.37	3.417%	$132.7564	$132.76	$132.75	$132.80
Purchase #6	$84.45	5.253%	$88.8862	$88.89	$88.90	$88.90
Purchase #7	$233.81	7.257%	$250.7776	$250.78	$250.80	$250.80
7 purchase totals =	$960.06		$1,034.0859	$1,034.09	$1,034.10	$1,034.20