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	$120.25	5.594%	$126.9768	$126.98	$127.00	$127.00
Purchase #2	$9.57	3.338%	$9.8894	$9.89	$9.90	$9.90
Purchase #3	$40.28	13.451%	$45.6981	$45.70	$45.70	$45.70
Purchase #4	$180.85	8.283%	$195.8298	$195.83	$195.85	$195.80
Purchase #5	$101.72	3.752%	$105.5365	$105.54	$105.55	$105.50
Purchase #6	$63.63	5.799%	$67.3199	$67.32	$67.30	$67.30
Purchase #7	$6.98	4.394%	$7.2867	$7.29	$7.30	$7.30
7 purchase totals =	$523.28		$558.5372	$558.55	$558.60	$558.50