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	$121.38	7.219%	$130.1424	$130.14	$130.15	$130.10
Purchase #2	$135.57	9.611%	$148.5996	$148.60	$148.60	$148.60
Purchase #3	$146.82	12.696%	$165.4603	$165.46	$165.45	$165.50
Purchase #4	$38.89	7.146%	$41.6691	$41.67	$41.65	$41.70
Purchase #5	$238.55	9.212%	$260.5252	$260.53	$260.55	$260.50
Purchase #6	$79.58	3.282%	$82.1918	$82.19	$82.20	$82.20
Purchase #7	$92.78	8.783%	$100.9289	$100.93	$100.95	$100.90
7 purchase totals =	$853.57		$929.5173	$929.52	$929.55	$929.50