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	$85.43	10.688%	$94.5608	$94.56	$94.55	$94.60
Purchase #2	$33.40	5.790%	$35.3339	$35.33	$35.35	$35.30
Purchase #3	$135.75	12.342%	$152.5043	$152.50	$152.50	$152.50
Purchase #4	$75.65	3.208%	$78.0769	$78.08	$78.10	$78.10
Purchase #5	$203.58	9.506%	$222.9323	$222.93	$222.95	$222.90
Purchase #6	$249.71	3.252%	$257.8306	$257.83	$257.85	$257.80
Purchase #7	$134.43	5.735%	$142.1396	$142.14	$142.15	$142.10
7 purchase totals =	$917.95		$983.3784	$983.37	$983.45	$983.30