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	$175.60	3.297%	$181.3895	$181.39	$181.40	$181.40
Purchase #2	$150.39	4.782%	$157.5816	$157.58	$157.60	$157.60
Purchase #3	$127.81	9.211%	$139.5826	$139.58	$139.60	$139.60
Purchase #4	$238.34	10.719%	$263.8877	$263.89	$263.90	$263.90
Purchase #5	$167.47	5.166%	$176.1215	$176.12	$176.10	$176.10
Purchase #6	$27.72	12.452%	$31.1717	$31.17	$31.15	$31.20
Purchase #7	$60.83	11.343%	$67.7299	$67.73	$67.75	$67.70
7 purchase totals =	$948.16		$1,017.4645	$1,017.46	$1,017.50	$1,017.50