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	$179.42	11.661%	$200.3422	$200.34	$200.35	$200.30
Purchase #2	$228.76	7.595%	$246.1343	$246.13	$246.15	$246.10
Purchase #3	$45.88	5.458%	$48.3841	$48.38	$48.40	$48.40
Purchase #4	$71.79	5.581%	$75.7966	$75.80	$75.80	$75.80
Purchase #5	$232.93	9.671%	$255.4567	$255.46	$255.45	$255.50
Purchase #6	$155.79	7.464%	$167.4182	$167.42	$167.40	$167.40
Purchase #7	$202.91	9.825%	$222.8459	$222.85	$222.85	$222.80
7 purchase totals =	$1,117.48		$1,216.3780	$1,216.38	$1,216.40	$1,216.30