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	$43.79	11.190%	$48.6901	$48.69	$48.70	$48.70
Purchase #2	$117.97	11.854%	$131.9542	$131.95	$131.95	$132.00
Purchase #3	$123.75	7.161%	$132.6117	$132.61	$132.60	$132.60
Purchase #4	$60.40	7.502%	$64.9312	$64.93	$64.95	$64.90
Purchase #5	$80.36	9.641%	$88.1075	$88.11	$88.10	$88.10
Purchase #6	$125.61	13.773%	$142.9103	$142.91	$142.90	$142.90
Purchase #7	$95.37	5.405%	$100.5247	$100.52	$100.50	$100.50
7 purchase totals =	$647.25		$709.7297	$709.72	$709.70	$709.70