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	$122.68	13.691%	$139.4761	$139.48	$139.50	$139.50
Purchase #2	$149.46	3.385%	$154.5192	$154.52	$154.50	$154.50
Purchase #3	$116.73	7.564%	$125.5595	$125.56	$125.55	$125.60
Purchase #4	$173.99	6.428%	$185.1741	$185.17	$185.15	$185.20
Purchase #5	$201.90	8.296%	$218.6496	$218.65	$218.65	$218.60
Purchase #6	$174.56	4.538%	$182.4815	$182.48	$182.50	$182.50
Purchase #7	$162.50	6.125%	$172.4531	$172.45	$172.45	$172.50
7 purchase totals =	$1,101.82		$1,178.3131	$1,178.31	$1,178.30	$1,178.40