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	$172.30	5.167%	$181.2027	$181.20	$181.20	$181.20
Purchase #2	$117.35	3.468%	$121.4197	$121.42	$121.40	$121.40
Purchase #3	$153.64	3.751%	$159.403	$159.40	$159.40	$159.40
Purchase #4	$161.25	13.204%	$182.5415	$182.54	$182.55	$182.50
Purchase #5	$248.94	10.654%	$275.4621	$275.46	$275.45	$275.50
Purchase #6	$30.89	7.366%	$33.1654	$33.17	$33.15	$33.20
Purchase #7	$139.66	11.618%	$155.8857	$155.89	$155.90	$155.90
7 purchase totals =	$1,024.03		$1,109.0801	$1,109.08	$1,109.05	$1,109.10