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	$241.65	3.564%	$250.2624	$250.26	$250.25	$250.30
Purchase #2	$248.94	4.574%	$260.3265	$260.33	$260.35	$260.30
Purchase #3	$79.67	6.811%	$85.0963	$85.10	$85.10	$85.10
Purchase #4	$54.53	3.402%	$56.3851	$56.39	$56.40	$56.40
Purchase #5	$93.80	10.303%	$103.4642	$103.46	$103.45	$103.50
Purchase #6	$75.43	4.545%	$78.8583	$78.86	$78.85	$78.90
Purchase #7	$228.78	4.254%	$238.5123	$238.51	$238.50	$238.50
7 purchase totals =	$1,022.80		$1,072.9051	$1,072.91	$1,072.90	$1,073.00