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	$132.65	3.582%	$137.4015	$137.40	$137.40	$137.40
Purchase #2	$128.69	3.623%	$133.3524	$133.35	$133.35	$133.40
Purchase #3	$25.87	13.451%	$29.3498	$29.35	$29.35	$29.30
Purchase #4	$140.38	7.800%	$151.3296	$151.33	$151.35	$151.30
Purchase #5	$184.37	8.674%	$200.3623	$200.36	$200.35	$200.40
Purchase #6	$240.71	8.452%	$261.0548	$261.05	$261.05	$261.10
Purchase #7	$101.72	9.543%	$111.4271	$111.43	$111.45	$111.40
7 purchase totals =	$954.39		$1,024.2775	$1,024.27	$1,024.30	$1,024.30