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	$230.25	8.758%	$250.4153	$250.42	$250.40	$250.40
Purchase #2	$158.75	5.696%	$167.7924	$167.79	$167.80	$167.80
Purchase #3	$30.30	5.202%	$31.8762	$31.88	$31.90	$31.90
Purchase #4	$135.61	13.123%	$153.4061	$153.41	$153.40	$153.40
Purchase #5	$132.58	5.666%	$140.092	$140.09	$140.10	$140.10
Purchase #6	$219.60	13.437%	$249.1077	$249.11	$249.10	$249.10
Purchase #7	$136.71	11.419%	$152.3209	$152.32	$152.30	$152.30
7 purchase totals =	$1,043.80		$1,145.0106	$1,145.02	$1,145.00	$1,145.00