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	$83.61	10.554%	$92.4342	$92.43	$92.45	$92.40
Purchase #2	$150.38	6.775%	$160.5682	$160.57	$160.55	$160.60
Purchase #3	$212.40	9.777%	$233.1663	$233.17	$233.15	$233.20
Purchase #4	$139.30	4.255%	$145.2272	$145.23	$145.25	$145.20
Purchase #5	$71.34	10.221%	$78.6317	$78.63	$78.65	$78.60
Purchase #6	$178.93	9.551%	$196.0196	$196.02	$196.00	$196.00
Purchase #7	$137.88	11.647%	$153.9389	$153.94	$153.95	$153.90
7 purchase totals =	$973.84		$1,059.9861	$1,059.99	$1,060.00	$1,059.90