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	$96.92	6.853%	$103.5619	$103.56	$103.55	$103.60
Purchase #2	$181.37	9.605%	$198.7906	$198.79	$198.80	$198.80
Purchase #3	$28.65	10.766%	$31.7345	$31.73	$31.75	$31.70
Purchase #4	$93.71	7.356%	$100.6033	$100.60	$100.60	$100.60
Purchase #5	$156.56	8.159%	$169.3337	$169.33	$169.35	$169.30
Purchase #6	$249.51	5.376%	$262.9237	$262.92	$262.90	$262.90
Purchase #7	$110.70	5.206%	$116.463	$116.46	$116.45	$116.50
7 purchase totals =	$917.42		$983.4107	$983.39	$983.40	$983.40