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	$210.46	4.477%	$219.8823	$219.88	$219.90	$219.90
Purchase #2	$31.52	7.725%	$33.9549	$33.95	$33.95	$34.00
Purchase #3	$37.56	11.541%	$41.8948	$41.89	$41.90	$41.90
Purchase #4	$161.69	10.543%	$178.737	$178.74	$178.75	$178.70
Purchase #5	$132.93	7.166%	$142.4558	$142.46	$142.45	$142.50
Purchase #6	$140.92	9.803%	$154.7344	$154.73	$154.75	$154.70
Purchase #7	$227.52	8.380%	$246.5862	$246.59	$246.60	$246.60
7 purchase totals =	$942.60		$1,018.2454	$1,018.24	$1,018.30	$1,018.30