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	$114.37	5.714%	$120.9051	$120.91	$120.90	$120.90
Purchase #2	$34.66	4.329%	$36.1604	$36.16	$36.15	$36.20
Purchase #3	$13.34	5.841%	$14.1192	$14.12	$14.10	$14.10
Purchase #4	$229.81	7.184%	$246.3196	$246.32	$246.30	$246.30
Purchase #5	$239.34	12.855%	$270.1072	$270.11	$270.10	$270.10
Purchase #6	$208.41	10.167%	$229.599	$229.60	$229.60	$229.60
Purchase #7	$127.34	13.243%	$144.2036	$144.20	$144.20	$144.20
7 purchase totals =	$967.27		$1,061.4141	$1,061.42	$1,061.35	$1,061.40