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	$115.93	13.371%	$131.431	$131.43	$131.45	$131.40
Purchase #2	$172.47	7.784%	$185.8951	$185.90	$185.90	$185.90
Purchase #3	$221.42	13.646%	$251.635	$251.64	$251.65	$251.60
Purchase #4	$214.31	7.289%	$229.9311	$229.93	$229.95	$229.90
Purchase #5	$158.40	6.396%	$168.5313	$168.53	$168.55	$168.50
Purchase #6	$5.75	7.796%	$6.1983	$6.20	$6.20	$6.20
Purchase #7	$88.81	7.528%	$95.4956	$95.50	$95.50	$95.50
7 purchase totals =	$977.09		$1,069.1174	$1,069.13	$1,069.20	$1,069.00