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	$210.38	5.369%	$221.6753	$221.68	$221.70	$221.70
Purchase #2	$209.80	10.424%	$231.6696	$231.67	$231.65	$231.70
Purchase #3	$128.30	6.372%	$136.4753	$136.48	$136.50	$136.50
Purchase #4	$192.42	4.121%	$200.3496	$200.35	$200.35	$200.30
Purchase #5	$59.65	11.389%	$66.4435	$66.44	$66.45	$66.40
Purchase #6	$83.66	3.553%	$86.6324	$86.63	$86.65	$86.60
Purchase #7	$104.38	4.715%	$109.3015	$109.30	$109.30	$109.30
7 purchase totals =	$988.59		$1,052.5472	$1,052.55	$1,052.60	$1,052.50