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	$64.89	11.721%	$72.4958	$72.50	$72.50	$72.50
Purchase #2	$242.49	9.636%	$265.8563	$265.86	$265.85	$265.90
Purchase #3	$20.51	11.614%	$22.892	$22.89	$22.90	$22.90
Purchase #4	$210.72	8.840%	$229.3476	$229.35	$229.35	$229.30
Purchase #5	$77.67	13.789%	$88.3799	$88.38	$88.40	$88.40
Purchase #6	$12.84	9.699%	$14.0854	$14.09	$14.10	$14.10
Purchase #7	$80.68	13.841%	$91.8469	$91.85	$91.85	$91.80
7 purchase totals =	$709.80		$784.9039	$784.92	$784.95	$784.90