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	$187.45	9.325%	$204.9297	$204.93	$204.95	$204.90
Purchase #2	$72.76	10.134%	$80.1335	$80.13	$80.15	$80.10
Purchase #3	$170.60	4.550%	$178.3623	$178.36	$178.35	$178.40
Purchase #4	$101.78	10.517%	$112.4842	$112.48	$112.50	$112.50
Purchase #5	$66.33	11.341%	$73.8525	$73.85	$73.85	$73.90
Purchase #6	$6.76	13.228%	$7.6542	$7.65	$7.65	$7.70
Purchase #7	$49.59	6.677%	$52.9011	$52.90	$52.90	$52.90
7 purchase totals =	$655.27		$710.3175	$710.30	$710.35	$710.40