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	$126.53	8.532%	$137.3255	$137.33	$137.35	$137.30
Purchase #2	$145.40	9.185%	$158.755	$158.76	$158.75	$158.80
Purchase #3	$151.62	8.448%	$164.4289	$164.43	$164.45	$164.40
Purchase #4	$114.49	3.577%	$118.5853	$118.59	$118.60	$118.60
Purchase #5	$6.76	4.849%	$7.0878	$7.09	$7.10	$7.10
Purchase #6	$211.39	4.172%	$220.2092	$220.21	$220.20	$220.20
Purchase #7	$189.93	3.231%	$196.0666	$196.07	$196.05	$196.10
7 purchase totals =	$946.12		$1,002.4583	$1,002.48	$1,002.50	$1,002.50