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	$179.65	7.699%	$193.4813	$193.48	$193.50	$193.50
Purchase #2	$103.32	8.344%	$111.941	$111.94	$111.95	$111.90
Purchase #3	$18.32	12.350%	$20.5825	$20.58	$20.60	$20.60
Purchase #4	$127.48	12.575%	$143.5106	$143.51	$143.50	$143.50
Purchase #5	$164.34	6.834%	$175.571	$175.57	$175.55	$175.60
Purchase #6	$159.73	11.615%	$178.2826	$178.28	$178.30	$178.30
Purchase #7	$28.30	11.387%	$31.5225	$31.52	$31.50	$31.50
7 purchase totals =	$781.14		$854.8915	$854.88	$854.90	$854.90