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	$229.32	7.676%	$246.9226	$246.92	$246.90	$246.90
Purchase #2	$71.27	10.157%	$78.5089	$78.51	$78.50	$78.50
Purchase #3	$85.30	10.792%	$94.5056	$94.51	$94.50	$94.50
Purchase #4	$103.97	4.638%	$108.7921	$108.79	$108.80	$108.80
Purchase #5	$199.60	13.602%	$226.7496	$226.75	$226.75	$226.70
Purchase #6	$249.77	5.653%	$263.8895	$263.89	$263.90	$263.90
Purchase #7	$73.55	12.587%	$82.8077	$82.81	$82.80	$82.80
7 purchase totals =	$1,012.78		$1,102.1760	$1,102.18	$1,102.15	$1,102.10