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	$111.52	7.450%	$119.8282	$119.83	$119.85	$119.80
Purchase #2	$90.38	11.129%	$100.4384	$100.44	$100.45	$100.40
Purchase #3	$68.76	7.451%	$73.8833	$73.88	$73.90	$73.90
Purchase #4	$237.66	5.811%	$251.4704	$251.47	$251.45	$251.50
Purchase #5	$212.99	10.263%	$234.8492	$234.85	$234.85	$234.80
Purchase #6	$102.42	11.679%	$114.3816	$114.38	$114.40	$114.40
Purchase #7	$235.34	4.643%	$246.2668	$246.27	$246.25	$246.30
7 purchase totals =	$1,059.07		$1,141.1179	$1,141.12	$1,141.15	$1,141.10