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	$79.93	10.821%	$88.5792	$88.58	$88.60	$88.60
Purchase #2	$154.31	8.236%	$167.019	$167.02	$167.00	$167.00
Purchase #3	$158.47	7.661%	$170.6104	$170.61	$170.60	$170.60
Purchase #4	$185.61	3.699%	$192.4757	$192.48	$192.50	$192.50
Purchase #5	$39.95	10.822%	$44.2734	$44.27	$44.25	$44.30
Purchase #6	$104.97	4.632%	$109.8322	$109.83	$109.85	$109.80
Purchase #7	$225.46	11.296%	$250.928	$250.93	$250.95	$250.90
7 purchase totals =	$948.70		$1,023.7179	$1,023.72	$1,023.75	$1,023.70