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	$38.28	5.390%	$40.3433	$40.34	$40.35	$40.30
Purchase #2	$131.30	9.296%	$143.5056	$143.51	$143.50	$143.50
Purchase #3	$232.60	12.655%	$262.0355	$262.04	$262.05	$262.00
Purchase #4	$173.71	6.818%	$185.5535	$185.55	$185.55	$185.60
Purchase #5	$28.69	6.659%	$30.6005	$30.60	$30.60	$30.60
Purchase #6	$174.26	4.741%	$182.5217	$182.52	$182.50	$182.50
Purchase #7	$192.75	12.665%	$217.1618	$217.16	$217.15	$217.20
7 purchase totals =	$971.59		$1,061.7219	$1,061.72	$1,061.70	$1,061.70