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	$227.40	5.304%	$239.4613	$239.46	$239.45	$239.50
Purchase #2	$206.82	4.703%	$216.5467	$216.55	$216.55	$216.50
Purchase #3	$189.51	13.748%	$215.5638	$215.56	$215.55	$215.60
Purchase #4	$128.28	7.311%	$137.6586	$137.66	$137.65	$137.70
Purchase #5	$11.78	4.597%	$12.3215	$12.32	$12.30	$12.30
Purchase #6	$69.53	5.639%	$73.4508	$73.45	$73.45	$73.50
Purchase #7	$123.33	5.633%	$130.2772	$130.28	$130.30	$130.30
7 purchase totals =	$956.65		$1,025.2799	$1,025.28	$1,025.25	$1,025.40