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	$98.51	4.226%	$102.673	$102.67	$102.65	$102.70
Purchase #2	$177.79	11.489%	$198.2163	$198.22	$198.20	$198.20
Purchase #3	$87.86	13.242%	$99.4944	$99.49	$99.50	$99.50
Purchase #4	$212.98	5.758%	$225.2434	$225.24	$225.25	$225.20
Purchase #5	$188.82	3.429%	$195.2946	$195.29	$195.30	$195.30
Purchase #6	$165.42	7.686%	$178.1342	$178.13	$178.15	$178.10
Purchase #7	$153.63	12.165%	$172.3191	$172.32	$172.30	$172.30
7 purchase totals =	$1,085.01		$1,171.3750	$1,171.36	$1,171.35	$1,171.30