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	$57.74	8.606%	$62.7091	$62.71	$62.70	$62.70
Purchase #2	$78.86	13.415%	$89.4391	$89.44	$89.45	$89.40
Purchase #3	$104.35	11.819%	$116.6831	$116.68	$116.70	$116.70
Purchase #4	$14.34	3.765%	$14.8799	$14.88	$14.90	$14.90
Purchase #5	$196.35	7.375%	$210.8308	$210.83	$210.85	$210.80
Purchase #6	$160.66	9.865%	$176.5091	$176.51	$176.50	$176.50
Purchase #7	$134.89	5.151%	$141.8382	$141.84	$141.85	$141.80
7 purchase totals =	$747.19		$812.8893	$812.89	$812.95	$812.80