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	$215.50	11.731%	$240.7803	$240.78	$240.80	$240.80
Purchase #2	$134.34	3.778%	$139.4154	$139.42	$139.40	$139.40
Purchase #3	$45.94	11.767%	$51.3458	$51.35	$51.35	$51.30
Purchase #4	$125.71	3.693%	$130.3525	$130.35	$130.35	$130.40
Purchase #5	$105.61	12.172%	$118.4648	$118.46	$118.45	$118.50
Purchase #6	$204.59	4.315%	$213.4181	$213.42	$213.40	$213.40
Purchase #7	$198.82	8.607%	$215.9324	$215.93	$215.95	$215.90
7 purchase totals =	$1,030.51		$1,109.7093	$1,109.71	$1,109.70	$1,109.70