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	$161.60	7.119%	$173.1043	$173.10	$173.10	$173.10
Purchase #2	$246.95	3.578%	$255.7859	$255.79	$255.80	$255.80
Purchase #3	$177.66	4.259%	$185.2265	$185.23	$185.25	$185.20
Purchase #4	$90.73	7.484%	$97.5202	$97.52	$97.50	$97.50
Purchase #5	$192.39	8.318%	$208.393	$208.39	$208.40	$208.40
Purchase #6	$12.72	11.115%	$14.1338	$14.13	$14.15	$14.10
Purchase #7	$138.49	8.859%	$150.7588	$150.76	$150.75	$150.80
7 purchase totals =	$1,020.54		$1,084.9225	$1,084.92	$1,084.95	$1,084.90