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	$196.42	6.709%	$209.5978	$209.60	$209.60	$209.60
Purchase #2	$184.29	4.808%	$193.1507	$193.15	$193.15	$193.20
Purchase #3	$97.35	11.701%	$108.7409	$108.74	$108.75	$108.70
Purchase #4	$141.96	12.321%	$159.4509	$159.45	$159.45	$159.50
Purchase #5	$250.38	11.215%	$278.4601	$278.46	$278.45	$278.50
Purchase #6	$131.40	6.227%	$139.5823	$139.58	$139.60	$139.60
Purchase #7	$50.54	9.134%	$55.1563	$55.16	$55.15	$55.20
7 purchase totals =	$1,052.34		$1,144.1390	$1,144.14	$1,144.15	$1,144.30