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	$227.90	6.517%	$242.7522	$242.75	$242.75	$242.80
Purchase #2	$40.90	10.828%	$45.3287	$45.33	$45.35	$45.30
Purchase #3	$29.53	4.616%	$30.8931	$30.89	$30.90	$30.90
Purchase #4	$122.78	9.738%	$134.7363	$134.74	$134.75	$134.70
Purchase #5	$211.58	8.639%	$229.8584	$229.86	$229.85	$229.90
Purchase #6	$163.92	13.163%	$185.4968	$185.50	$185.50	$185.50
Purchase #7	$101.66	9.736%	$111.5576	$111.56	$111.55	$111.60
7 purchase totals =	$898.27		$980.6231	$980.63	$980.65	$980.70