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	$91.97	6.578%	$98.0198	$98.02	$98.00	$98.00
Purchase #2	$14.78	6.430%	$15.7304	$15.73	$15.75	$15.70
Purchase #3	$139.78	11.510%	$155.8687	$155.87	$155.85	$155.90
Purchase #4	$115.51	13.472%	$131.0715	$131.07	$131.05	$131.10
Purchase #5	$230.29	3.354%	$238.0139	$238.01	$238.00	$238.00
Purchase #6	$156.61	7.513%	$168.3761	$168.38	$168.40	$168.40
Purchase #7	$249.94	8.687%	$271.6523	$271.65	$271.65	$271.70
7 purchase totals =	$998.88		$1,078.7327	$1,078.73	$1,078.70	$1,078.80