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	$128.28	11.280%	$142.75	$142.75	$142.75	$142.80
Purchase #2	$5.84	12.488%	$6.5693	$6.57	$6.55	$6.60
Purchase #3	$52.84	12.262%	$59.3192	$59.32	$59.30	$59.30
Purchase #4	$170.78	11.611%	$190.6093	$190.61	$190.60	$190.60
Purchase #5	$81.32	6.845%	$86.8864	$86.89	$86.90	$86.90
Purchase #6	$85.92	5.370%	$90.5339	$90.53	$90.55	$90.50
Purchase #7	$20.94	4.256%	$21.8312	$21.83	$21.85	$21.80
7 purchase totals =	$545.92		$598.4993	$598.50	$598.50	$598.50