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	$202.47	9.511%	$221.7269	$221.73	$221.75	$221.70
Purchase #2	$227.39	10.382%	$250.9976	$251.00	$251.00	$251.00
Purchase #3	$211.90	6.552%	$225.7837	$225.78	$225.80	$225.80
Purchase #4	$55.84	6.139%	$59.268	$59.27	$59.25	$59.30
Purchase #5	$198.56	7.137%	$212.7312	$212.73	$212.75	$212.70
Purchase #6	$29.76	10.425%	$32.8625	$32.86	$32.85	$32.90
Purchase #7	$52.99	6.578%	$56.4757	$56.48	$56.50	$56.50
7 purchase totals =	$978.91		$1,059.8456	$1,059.85	$1,059.90	$1,059.90