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	$106.73	10.255%	$117.6752	$117.68	$117.70	$117.70
Purchase #2	$136.85	4.842%	$143.4763	$143.48	$143.50	$143.50
Purchase #3	$42.54	7.212%	$45.608	$45.61	$45.60	$45.60
Purchase #4	$169.41	5.831%	$179.2883	$179.29	$179.30	$179.30
Purchase #5	$67.61	7.245%	$72.5083	$72.51	$72.50	$72.50
Purchase #6	$205.61	10.693%	$227.5959	$227.60	$227.60	$227.60
Purchase #7	$100.36	9.166%	$109.559	$109.56	$109.55	$109.60
7 purchase totals =	$829.11		$895.7110	$895.73	$895.75	$895.80