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	$119.42	7.147%	$127.9549	$127.95	$127.95	$128.00
Purchase #2	$34.41	13.872%	$39.1834	$39.18	$39.20	$39.20
Purchase #3	$157.69	9.268%	$172.3047	$172.30	$172.30	$172.30
Purchase #4	$36.40	13.136%	$41.1815	$41.18	$41.20	$41.20
Purchase #5	$182.82	9.681%	$200.5188	$200.52	$200.50	$200.50
Purchase #6	$150.40	6.351%	$159.9519	$159.95	$159.95	$160.00
Purchase #7	$86.69	13.465%	$98.3628	$98.36	$98.35	$98.40
7 purchase totals =	$767.83		$839.4580	$839.44	$839.45	$839.60