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	$115.85	9.629%	$127.0052	$127.01	$127.00	$127.00
Purchase #2	$73.59	6.593%	$78.4418	$78.44	$78.45	$78.40
Purchase #3	$33.88	3.868%	$35.1905	$35.19	$35.20	$35.20
Purchase #4	$98.95	10.264%	$109.1062	$109.11	$109.10	$109.10
Purchase #5	$208.75	6.665%	$222.6632	$222.66	$222.65	$222.70
Purchase #6	$225.45	4.657%	$235.9492	$235.95	$235.95	$235.90
Purchase #7	$88.93	6.208%	$94.4508	$94.45	$94.45	$94.50
7 purchase totals =	$845.40		$902.8069	$902.81	$902.80	$902.80