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	$142.69	7.629%	$153.5758	$153.58	$153.60	$153.60
Purchase #2	$69.49	12.671%	$78.2951	$78.30	$78.30	$78.30
Purchase #3	$164.50	3.202%	$169.7673	$169.77	$169.75	$169.80
Purchase #4	$211.98	3.214%	$218.793	$218.79	$218.80	$218.80
Purchase #5	$236.50	12.240%	$265.4476	$265.45	$265.45	$265.40
Purchase #6	$38.90	3.395%	$40.2207	$40.22	$40.20	$40.20
Purchase #7	$242.81	8.546%	$263.5605	$263.56	$263.55	$263.60
7 purchase totals =	$1,106.87		$1,189.6600	$1,189.67	$1,189.65	$1,189.70