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	$105.94	12.544%	$119.2291	$119.23	$119.25	$119.20
Purchase #2	$95.54	10.207%	$105.2918	$105.29	$105.30	$105.30
Purchase #3	$119.59	6.851%	$127.7831	$127.78	$127.80	$127.80
Purchase #4	$169.48	9.458%	$185.5094	$185.51	$185.50	$185.50
Purchase #5	$127.48	12.290%	$143.1473	$143.15	$143.15	$143.10
Purchase #6	$196.68	8.294%	$212.9926	$212.99	$213.00	$213.00
Purchase #7	$109.74	3.498%	$113.5787	$113.58	$113.60	$113.60
7 purchase totals =	$924.45		$1,007.5320	$1,007.53	$1,007.60	$1,007.50