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	$123.73	7.208%	$132.6485	$132.65	$132.65	$132.60
Purchase #2	$162.67	7.472%	$174.8247	$174.82	$174.80	$174.80
Purchase #3	$127.89	8.765%	$139.0996	$139.10	$139.10	$139.10
Purchase #4	$238.37	11.291%	$265.2844	$265.28	$265.30	$265.30
Purchase #5	$169.46	4.364%	$176.8552	$176.86	$176.85	$176.90
Purchase #6	$159.72	3.251%	$164.9125	$164.91	$164.90	$164.90
Purchase #7	$175.80	11.447%	$195.9238	$195.92	$195.90	$195.90
7 purchase totals =	$1,157.64		$1,249.5487	$1,249.54	$1,249.50	$1,249.50