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	$219.82	6.681%	$234.5062	$234.51	$234.50	$234.50
Purchase #2	$234.89	10.503%	$259.5605	$259.56	$259.55	$259.60
Purchase #3	$47.84	4.796%	$50.1344	$50.13	$50.15	$50.10
Purchase #4	$154.80	7.189%	$165.9286	$165.93	$165.95	$165.90
Purchase #5	$69.81	12.796%	$78.7429	$78.74	$78.75	$78.70
Purchase #6	$131.35	8.261%	$142.2008	$142.20	$142.20	$142.20
Purchase #7	$152.93	9.686%	$167.7428	$167.74	$167.75	$167.70
7 purchase totals =	$1,011.44		$1,098.8162	$1,098.81	$1,098.85	$1,098.70