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	$208.67	6.708%	$222.6676	$222.67	$222.65	$222.70
Purchase #2	$60.80	3.379%	$62.8544	$62.85	$62.85	$62.90
Purchase #3	$168.89	12.353%	$189.753	$189.75	$189.75	$189.80
Purchase #4	$18.37	7.658%	$19.7768	$19.78	$19.80	$19.80
Purchase #5	$77.59	6.477%	$82.6155	$82.62	$82.60	$82.60
Purchase #6	$70.86	12.715%	$79.8698	$79.87	$79.85	$79.90
Purchase #7	$239.30	12.151%	$268.3773	$268.38	$268.40	$268.40
7 purchase totals =	$844.48		$925.9144	$925.92	$925.90	$926.10